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Brown, who won a 2010 special Senate election in Massachusetts and then lost his bid for a full term in last month's general election to Democrat Elizabeth Warren, 63, would be the favorite to gain his party's nomination for another try.
"The nomination is his, if he wants it," said Jeffrey Berry, a political science professor at Tufts University in Medford, Mass. "There is no firebrand conservative here who could overtake him. He would, however, be no shoo-in for the special election."
If Kerry's appointment by President Barack Obama wins confirmation, Gov. Deval Patrick will appoint someone to hold the Senate seat until a special election is held to select a successor through the 2014 election.
Patrick said Friday he wouldn't announce a Senate replacement "until the confirmation process is complete" and Kerry has resigned his seat, according to a transcript of his remarks in Boston. State law calls for the special election to be held between 145 to 160 days following the vacancy. The special election would be preceded by party primaries.
"There really is no way to predict who will be the favorite, if Vicki Kennedy doesn't run," said Berry of the Democratic nomination race. "There is not much in the way of visible campaigning so far."
Other Democrats receiving attention in the Massachusetts media as possible candidates include former governor and 1988 presidential nominee Michael S. Dukakis and Edward M. Kennedy Jr., the son of the late senator and a Connecticut resident. Also mentioned are actor Ben Affleck and Margaret Marshall, the retired chief justice of the Supreme Judicial Court of Massachusetts, and three of the state's House members -- Edward Markey, Michael Capuano and Stephen Lynch.
Retiring Mass. Rep. Barney Frank hasn't ruled out accepting the interim appointment until a special election could be held next year. Frank told Politico in a Dec. 19 interview that Patrick "ought to be free to make whatever choices he makes." He said accepting or rejecting offers that have yet to be made would be "presumptuous."
"It is curious how both parties appear to be looking at the special through the lens of 2010," said Duffy. "It's almost as if they are preparing to fight the last war all over again. It will be a different race, even if some of the faces are the same."
Duffy said a main difference is that Democrats won't again take victory in a special election for granted, as they did during most of the brief campaign in the 2010 vote. Also, Patrick's interim appointment for Kerry's seat could be someone who will then run in the special election.
He said Friday that, for Kerry's seat, "I expect to appoint someone who does not plan to run for the seat because practically I think that's going to be hard for that person to do successfully." Still, he didn't definitively rule out naming someone who then becomes a candidate.
If Brown seeks the Republican nomination, Duffy said he will need to run a different kind of race than in 2010. "He has now served in the Senate and has a voting record," she said. "It is pretty hard for him to run as an outsider."
In the January 2010 special election, Brown defeated Democratic state Attorney General Martha Coakley, 52 percent to 47 percent -- an upset that gained national attention.
Obama had flown to Massachusetts the weekend before the vote to rally Democrats, saying his party's priorities would be threatened by Brown, who had pledged to vote against Democratic health-care legislation and a proposed fee on large financial institutions.
The race drew outside political spending from both sides. The Tea Party Express, which opposed Obama's health-care plan, strongly backed Brown.
Once in office, Brown emphasized his independence from the Republican Party, which was aimed at shoring up his support in Massachusetts. In his 2012 re-election bid, he sought to appeal to Obama backers by using images in ads of himself with the president.
Warren Win Brown lost to Warren, whose attacks on Wall Street helped fuel her political ascent. She became the first woman elected as a U.S. senator from Massachusetts. She is a Harvard University professor who helped Obama establish the Consumer Financial Protection Bureau, created by the Dodd-Frank law that set new rules for Wall Street.
To boost her candidacy, Democrats gave Warren a prime-time speaking role at their national convention in September. She also attacked Brown for voting against a measure making it easier for women to sue for equal pay, health insurance coverage for birth control and one of Obama's Supreme Court nominees.
Warren, who will take office in January, beat Brown 54 percent to 46 percent.
In general elections, the state tends to vote overwhelmingly Democratic. Mitt Romney, the 2012 Republican presidential nominee, won just 38 percent in the state, despite strong Massachusetts ties that included being a former governor, basing his campaign headquarters in Boston and owning property.
Brown had been aided in his 2010 victory by relatively low voter turnout, which could again work to his advantage in a 2013 special election.
In last month's Senate race, more than 3.1 million ballots were cast. In the 2010 special election, the turnout was more than 2.2 million.
Kerry, 69, was the 2004 Democratic presidential nominee, losing that race to incumbent George W. Bush. Kerry was first elected to the Senate in 1984 and won his fifth term in 2008 with 66 percent of the vote.
In the new Senate that convenes in January and will include Kerry, Democrats will control 55 seats to 45 for Republicans.