"Super PAC" Role Grows for Republican Campaigns Weeks of intense campaigning in the early nominating states have left the leading Republican presidential candidates increasingly dependent on millions of dollars spent on their behalf by outside "super PACs," reports filed with the Federal Election Commission on Monday showed. Mitt Romney turned his attention to Cincinnati on Monday. The Republican presidential candidates have been spending heavily. Jeff Swensen for The New York Times Rick Santorum campaigned in Steubenville, Ohio Mitt Romney's campaign spent $19 million during January, almost three times as much as the $6.5 million he raised. He ultimately won two states, New Hampshire and Florida, ending the month with less than $8 million in cash on hand. Newt Gingrich raised nearly as much, $5.6 million, and spent close to $6 million. Rick Santorum, who enjoyed a surge of grass-roots donations after being declared the victor in Iowa, raised $4.5 million, as did Representative Ron Paul of Texas - amounts that still leave Mr. Romney in the lead but no longer in a class by himself when it comes to raising money. The super PAC backing Mr. Romney, Restore Our Future, raised $6.6 million in January and spent close to $14 million, much of it on advertisements battering Mr. Gingrich in Iowa and Florida. A super PAC backing Mr. Gingrich raised much more that month - almost $11 million - and spent most of it on attack advertisements against Mr. Romney in South Carolina, where Mr. Gingrich ultimately won, and in Florida, where Mr. Romney prevailed. The spending reports revealed the breadth and power of super PACs as the campaign hits a critical and perhaps decisive period, with outside groups poised to pick up a growing share of political spending during the costly primary battle that lies ahead. Bolstered by Mr. Romney's extraordinarily high burn rate, the campaigns spent about $5 million more during January than the super PACs supporting them. But over all, super PACs backing the four leading Republican contenders raised $22.1 million in January, slightly more than the candidates themselves, and ended the month with $19.4 million in cash on hand, about $5 million more than the candidates had. Most of that money came in six- and seven-figure checks from just a few dozen individuals and corporations - the billionaire casino executive Sheldon Adelson, the mutual fund investor Foster S. Friess, and the Texas industrialist Harold C. Simmons, among others - who have exploited recent court rulings and regulatory shifts to exert unprecedented influence over their party's choice of presidential nominee. Restore Our Future, the super PAC backing Mr. Romney, entered February with $16.3 million in cash on hand, money that has already underwritten an early run of attack advertisements against Mr. Santorum, whose victories in Colorado, Minnesota and Missouri this month have made him the chief target for Mr. Romney's attacks. Mr. Romney could be even more dependent on Restore Our Future money than he was last month: while he has raised far more than other Republican candidates, he has spent heavily without taking a clear lead in the race. Moreover, Mr. Romney is "maxing out" the donors to his campaign - taking the maximum $2,500 contribution allowed by federal law for the primary - faster than any of the leading candidates of either party during the last two races, according to analysis by The New York Times. Through the end of December, Mr. Romney had raised $2,500 from more than 14,000 donors, representing about 44 percent of all of his contributors. About 5 percent of Mr. Paul's donors, 14 percent of Mr. Gingrich's donors, and 30 percent of Mr. Santorum's donors had maxed out, meaning that the vast majority of their contributors can continue to give more money - in most cases significantly more - this year. As his campaign prepares for a potentially long fight for the nomination, Mr. Romney has stepped up his fund-raising events in strongholds like Washington and New York and begun prospecting elsewhere for supporters. During a campaign visit to Cincinnati on Monday, Mr. Romney made time for an evening stop at the Great American Tower, where local donors said they would raise more than $600,000 for him. "We are very pleased with the continued support we have received from Americans across the country who want to see real change in Washington," Spencer Zwick, Mr. Romney's national finance chairman, said in a statement. We have exceeded our fund-raising goals and are on track with spending plans. We are the only campaign who has the organization and resources to go the distance of a long primary process. Though other candidates appear to have more robust grassroots fund-raising networks than Mr. Romney, they also ended January with far less money in the bank. Mr. Gingrich had about $1.8 million - and nearly as much debt. Mr. Santorum ended January with less than $1.5 million on hand, though his campaign said he raised at least $3 million in grass-roots contributions after his triple victories this month. Mr. Paul had about $1.6 million. Griff Palmer and Jeff Zeleny contributed reporting.