State Representative Daniel B. Winslow, a former judge and onetime aide to Governor Mitt Romney, said Thursday he is entering the special election for the US Senate, the first Republican to officially declare his candidacy. 
 
 “I’m in,” Winslow said in a telephone interview. He had said earlier this week that he was “99 percent” certain he would run. 
 
 Winslow said he has donated $100,000 of his own money to jumpstart his campaign, which he estimated will cost between $4 million and $6 million. 
 
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 On Monday, he said, he is flying to Washington to meet with Republicans on Capitol Hill and with the National Republican Senatorial Committee, which controls much of the party’s national fundraising. Nex month, Winslow said, he will resign from his law firm, Proskauer, where he is senior counsel in the litigation department. 
 
 “I’m going to be 100 percent running for the US Senate,” Winslow said. “This is a heavy lift. I’m going to give this race everything I’ve got.” 
 
 Winslow, 54, is a second-term state representative from Norfolk who served as Romney’s chief legal counsel from 2001 to 2005. Before that, he was a district court judge. 
 
 “I have a proven record of respect for Second Amendment constitutional freedoms,” Winslow wrote in an email announcing his candidacy to party activists and supporters. “My experience as a fiscal conservative and problem solver is experience we need in Washington DC. Our future depends on getting this right.” 
 
 Many of the bigger-name Republicans, including former senator Scott Brown, former governor Wiliam F. Weld, and former lieutenant governor Kerry Healey, have taken themselves out of consideration. 
 
 Other Republicans considering the race include Senate Minority Leader Bruce E. Tarr, former congressional candidate Sean Bielat, and Gabriel E. Gomez, a private equity investor and former Navy SEAL. Jon Fetherston, a former chair of the Ashland Board of Selectman, is also planning to run for the seat. 
 
 Two US House members, Stephen F. Lynch and Edward J. Markey, are running on the Democratic side. 
 
 To qualify for the April 30 ballot, candidates will have to gather 10,000 certified signatures by Feb. 27. That hurdle may weed out many of the little-known candidates who cannot raise substantial sums of money. Winslow said he plans to use volunteers and paid staff to collect signatures and has no doubt he can make the ballot. ||||| State Rep. Daniel B. Winslow became the first Republican to officially join the U.S. Senate special election to replace Secretary of State John F. Kerry yesterday, saying he is “110 percent” committed to what will be a short but potentially bruising race. 
 
 “I’m going to give this everything I’ve got, with all that I have, because the crisis confronting our country demands nothing less,” Winslow (R-Norfolk) said. “I am confident I am going to be on the Republican ballot.” 
 
 Winslow is the first Republican to officially enter the race after Democratic U.S. Reps. Stephen F. Lynch and Edward J. Markey announced they were running. Gabriel Gomez, a Cohasset businessman, and state Senate Minority Leader Bruce E. Tarr (R-Gloucester) are also mulling a run. 
 
 Tarr said he will make a decision as to whether he is in or out of the race “no later than Monday.” 
 
 Joining the special election has become increasingly difficult with every day that passes because candidates must collect 10,000 signatures before Feb. 27 to get on the ballot. 
 
 Winslow, who launched an exploratory committee Tuesday, said he is confident he can get all the signatures, even though candidates usually must collect up to 20,000 signatures in case some aren’t accepted. 
 
 “We’re going to use a combination of paid vendors and an army of volunteers to get this done,” said Winslow, who once served as former Gov. Mitt Romney’s chief legal counsel. 
 
 Republicans have been scrambling to find a candidate since former U.S. Sen. Scott Brown announced last Friday that he isn’t running.
– After being rebuffed by Scott Brown, Tagg Romney, William Weld, and Kerry Healey, Massachusetts Republicans finally have at least one candidate for Senate. State Rep. Daniel Winslow, who had previously said that he was "99% certain" he'd run, yesterday told the Boston Globe he was "going to be 100% running for the US Senate." Winslow chipped in $100,000 of his own money to start the campaign, but that's a fraction of the $4 million to $6 million he estimates the venture will cost. Before becoming a state rep, Winslow served as chief legal counsel to Mitt Romney and as a district court judge. He'll fly to Washington on Monday to meet with the National Republican Senatorial Committee, presumably in the hopes of securing more funding. At least three other Republicans are also publicly considering runs, but every day they delay getting in will make that prospect harder, the Boston Herald points out, because candidates need 10,000 signatures by Feb. 27—and generally shoot for 20,000 in case some are challenged.