NEW YORK/WASHINGTON (Reuters) - Republican presidential hopeful Donald Trump’s campaign raised $3.1 million from donors in May, more than doubling previous monthly hauls as he began soliciting donations to battle Democratic rival Hillary Clinton. 
 
 Republican U.S. Presidential candidate Donald Trump speaks at a campaign rally in Phoenix, Arizona, June 18, 2016. REUTERS/Nancy Wiechec 
 
 But with spending that outpaced inflows, the New York real estate magnate’s campaign began June with just $1.29 million in cash, putting it well-behind Clinton’s $42 million war chest, according to federal disclosures filed late on Monday. 
 
 Clinton’s campaign raised $26 million in May. 
 
 The figures underscore the huge money advantage Clinton is hoping to enjoy leading into the Nov. 8 election, one that could allow her a large staff and millions of dollars of television and digital ads in battleground states. 
 
 Trump, who has self-funded most of his campaign and only held his first general election fundraiser on May 25, is betting he can run a race that builds on his low-spending, insurgent primary operation. 
 
 Trump’s surrogates, however, have said the cash is now “pouring in” for the general election. For months the biggest cash injections into Trump’s campaign coffers were from his personal bank accounts. He has loaned his campaign $46 million since launching last year. 
 
 Trump may still have several hurdles to cross before convincing deep-pocketed donors to write the kind of checks that would make him competitive with Clinton’s campaign bank account. 
 
 Trump donors, allies and other Republican operatives continue to express concerns about his campaign operation, which has been dogged by internal battles, a threadbare campaign infrastructure of about 30 paid staffers, and a barely existent fundraising apparatus. 
 
 On Monday, Trump fired his campaign manager, Corey Lewandowski, who had been tasked with overseeing the campaign’s fundraising arm. 
 
 The primary Super PAC supporting Trump, Great America PAC, reported raising $1.4 million in May - accounting for most of the $2.5 million the group has raised this year. The PAC had $500,971 cash remaining at the beginning of June. 
 
 Clinton’s cash advantage has been fueled in part by the Super PAC supporting her. Priorities USA raised $12 million in the last month, ending May with a $52 million in cash. Three unions, AFT Solidarity, Liuna Building America and International Union of Operating Engineers, each gave $1 million. 
 
 The group has largely been tasked with attacking Trump. And so far, they have spent more than $5.7 million this year on television ads alone attacking the Republican. 
 
 (In fifth paragraph, this story corrects the date of first Trump general election fundraiser to May 25) ||||| Moreover, Mr. Trump’s surge is coming very late in the campaign, at a point where advertising rates climb and the chance to invest in a long-term digital and campaign infrastructure is long past. 
 
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 And Mrs. Clinton’s own fund-raising operation is rapidly expanding as well. In a Twitter post on Wednesday, a spokesman for Mrs. Clinton said that her campaign and a joint fund-raising operation with the Democratic National Committee had $102 million on hand, not including cash held directly by the party. 
 
 But Mr. Trump’s announcement suggests that after months of dithering and false starts, he has begun to exploit an opportunity: marrying his powerful credibility among grass-roots Republicans with targeted small-donor fund-raising, particularly online, where Mr. Trump’s website features buttons soliciting $50, $25 and even $10 contributions. 
 
 At the end of May, Mr. Trump reported barely more than $1.3 million in cash, alarming Republicans, who feared a financial rout by Mrs. Clinton. 
 
 Mitt Romney, the party’s 2012 nominee and a wealthy man in his own right, was never able to stoke intense enthusiasm among small donors and relied disproportionately on big ones. During July of that year, for example, Mr. Romney and the Republican National Committee reported raising a total of just $19 million from contributions of less than $200. 
 
 Mr. Trump was able to ramp up quickly in part through a digital operation set up by the R.N.C. since that campaign. Even before Mr. Trump was the nominee, the party built out its email list and tested ways of targeting small donors. 
 
 With that in place, party officials unleashed a pent-up desire by rank-and-file Republicans to donate to a candidate who has bluntly attacked lobbyists and big donors. While Mr. Trump accepted online donations during the primary season, he did not send out an email solicitation until late June — which brought in $3 million alone, an indication of the well of money available to him. 
 
 The campaign has also raised money by promising to match small donations out of Mr. Trump’s pocket, a tactic available only to wealthy candidates. 
 
 “There was always that potential, but you didn’t have candidates who were as uniquely positioned in the same way that Trump is,” said Patrick Ruffini, a Republican strategist who ran digital fund-raising at the Republican National Committee under President George W. Bush. 
 
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 But Mr. Trump’s surge also emphasizes the complication for Republicans in having him at the head of their party. He is relying more on small-donor fund-raising in part because he has faced opposition from some of the party’s biggest patrons, such as Meg Whitman, a California business executive, who said Monday that she was so disgusted with Mr. Trump that she would vote for Mrs. Clinton. 
 
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 To bolster his low-dollar fund-raising, Mr. Trump and his team are now working to assuage the broader pool of affluent Republican donors and fund-raisers. In recent weeks, Mr. Trump has laid off his criticisms of the party’s donor class and scheduled an array of formal fund-raising events for Republican donors in money centers like Florida and New York. 
 
 Moreover, even as his name and followers are helping fund Republican get-out-the-vote efforts around the country, Mr. Trump is feuding with the party’s senior leadership, pointedly refusing to endorse prominent Republicans facing Trump-inspired primary opponents, such as the one challenging Representative Paul D. Ryan of Wisconsin, the House speaker. 
 
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 And it is the Republican National Committee that is providing much of the technical expertise that has allowed Mr. Trump to quickly increase his low-dollar fund-raising, some Republican officials said. 
 
 Even as relations fray between Mr. Trump and some fellow Republicans, the party and Mr. Trump each needs the other. And Mr. Trump, as the nominee and the fund-raising tent pole for the party, may have the upper hand. 
 
 “Under normal circumstances, the party would have money as leverage,” Mr. Ruffini said. “They could cut off fund-raising to a candidate who misbehaves. And that leverage has been taken completely away.” ||||| Republican presidential candidate Donald Trump speaks during a campaign rally Tuesday in Sanford, Fla. Photo: Evan Vucci/Associated Press 
 
 Presidential nominee Donald Trump is slowing his high-dollar fundraising operation with the Republican Party, with no major fundraising events featuring the candidate planned for the final two weeks of the election, according to his finance chairman. 
 
 “We are no longer doing formal, sit-down fundraising events,” Trump finance chairman Steven Mnuchin said in an interview. He said the campaign had “always planned” not to deploy Mr. Trump to fundraisers in the last weeks of the election, and to instead focus on holding rallies and “winning the election.” 
 
 The final formal fundraiser for Trump Victory—a joint fundraising committee between the campaign, the Republican National Committee and state parties—was held Oct. 19, the day of the final presidential debate in Las Vegas, as first reported by the Washington Post. Mr. Trump also attended a fundraising event Monday at Mar-A-Lago in Palm Beach, Fla. 
 
 Mr. Mnuchin said the campaign will continue to do “informal fundraising” for the committee in coming weeks, which could include some events, and to raise money online. He declined to comment on whether Mr. Trump’s surrogates would headline any fundraisers in the coming weeks, but told the Post there was “virtually nothing planned.” 
 
 Later Tuesday, a spokeswoman for the Trump campaign said fundraising for Trump Victory would not be slowing in the final weeks. The spokeswoman, Jessica Ditto, said there were “a few [fundraisers] coming up” featuring surrogates but said she could not comment on specifics. A second spokesman, Jason Miller, said: “All fundraising, large and small including our Victory effort, will continue through the end of the election.” 
 
 It is not unusual for presidential candidates to step away from fundraising in the final weeks of an election. Democratic nominee Hillary Clinton is also slowing her personal fundraising activity in the final two weeks, with her last fundraiser scheduled for Tuesday. But campaigns typically plan to deploy surrogates in the candidate’s place—Mrs. Clinton’s campaign has scheduled around 40 fundraisers featuring surrogates for the final sprint to Election Day. 
 
 Mr. Trump’s slowed fundraising plans come as he lags behind Mrs. Clinton, both financially and in public-opinion polls. He entered September with half as much money in his campaign and joint fundraising committee bank accounts as Mrs. Clinton—$75 million to her $150 million. A Real Clear Politics average of recent national polls found Mrs. Clinton with a lead of more than 5 percentage points. 
 
 In reducing Mr. Trump’s high-dollar fundraising efforts, the campaign is also slowing fundraising for the Republican National Committee, which drew the majority of the funds raised for Trump Victory. Trump Victory—which can accept checks of up to $450,000 per person—in the third quarter raised $61 million. It transferred just $8.6 million to Mr. Trump’s campaign, and $28.7 million to the RNC. 
 
 Mr. Mnuchin said the campaign’s move wasn't “cutting off cash to the party,” and said the campaign will keep raising money with the RNC. He added that the campaign continues to raise money online and had seen a “record pace” so far this month. Mr. Trump will disclose fundraising for the first three weeks of October on Thursday. 
 
 “The RNC continues to fundraise for the entire GOP ticket,” said Lindsey Walters, a spokeswoman for the RNC. 
 
 Related Video The Trump campaign, in a recent letter to donors, explained how their candidate can win in the Electoral College. Is it a plausible path to victory? WSJ’s Jason Bellini has #TheShortAnswer. 
 
 Funds raised online for a second joint fundraising committee with the RNC, called Trump Make America Great Again, are largely allocated to the campaign rather than the party, with just 20% of each individual’s donations going to the party. 
 
 Mr. Mnuchin said the campaign is confident it has enough resources for the final weeks of the election. “We have more than enough money to support the ground campaign,” he said. 
 
 Mr. Trump’s ground game, however, has lagged far behind Mrs. Clinton’s, as he has relied largely on the RNC’s efforts. In September, he paid about 220 staffers, his Federal Election Commission filing showed, compared with 815 paid by Mrs. Clinton. 
 
 Mr. Trump has also said he would donate $100 million to his campaign, but has only given $56 million so far. It is unclear whether he plans to donate another $44 million. 
 
 Write to Rebecca Ballhaus at Rebecca.Ballhaus@wsj.com
– After a week full of headlines likely to have Donald Trump's advisers tearing their hair out, there's a bright spot for his campaign: He's narrowing the fundraising gap with Hillary Clinton, helped by a Bernie Sanders-style flood of small donations, NPR reports. The Trump campaign says it and joint fundraising committees raised $82 million in July—including $2 million from Trump himself—compared to around $90 million for Clinton, who ended the month with $58 million on hand, compared to $37 million for Trump, whose campaign was $40 million behind Clinton at the beginning of June, with just $1.3 million on hand. The Trump campaign says the bulk of the cash has come from small donations, most of them made online, reports the New York Times, which notes that this is a big change for a campaign that was "largely funded by hat and T-shirt sales and by Mr. Trump's wallet" until recently. "We are extremely proud of our 69% growth in small-dollar donations, which shows the broad-based support of over 1 million donors across America," says Steven Mnuchin, Trump's finance chairman, per CNN. Small donors may be Trump's only chance of closing the fundraising gap: Major GOP donors and fundraisers have been steering clear of his campaign, including Meg Whitman, who says she will raise funds for Clinton instead.