WASHINGTON — Democrats haven't found a solid challenger to GOP Sen. Scott Brown in liberal Massachusetts next year, stoking concerns the party could blow its best shot to take back the seat held for nearly a half-century by the late Sen. Edward Kennedy.
It's a seat close to Democrats' hearts, still raw from their humiliating loss to the upstart Brown in 2010.
The senator's widow, Vicki Kennedy, has flatly ruled out running. So did former Rep. Joe Kennedy, who joked he was "feeling ill all of a sudden" when reporters recently asked him about challenging Brown.
The state's leading Democrat, Gov. Deval Patrick, insists he's not interested. Former Rep. Martin Meehan, flush with $4.8 million in campaign cash, has rejected pleas from party officials to jump in.
Boston Mayor Thomas Menino, who rarely minces words, described Brown's prospects bluntly.
"There's nobody that can beat him," he told the Boston Herald recently.
With a crowded field of lesser-known candidates expected to run, Democrats fret that a long, costly and divisive primary could sink their hopes of reclaiming a seat they feel they never should have lost. Democrats are facing a tough fight in 2012 to hang onto their slim majority in the Senate.
"The looming liability right now for the Democrats is to go through a bloody, messy and expensive primary and then turn around with just six weeks to take on Scott Brown," said Mary Anne Marsh, a Democratic analyst in Boston. "So that's why Democrats have to think long and hard about who is running and trying to solidify behind someone who has the best shot at beating Scott Brown."
Rep. Michael Capuano, a potential challenger whose district includes Harvard Square and Cambridge, said rallying behind a single candidate would boost his party's chances considerably.
"The Democratic Party has to be totally, 100 percent unified in order to do it," said Capuano. "The bottom line is, yeah, he's a strong candidate by every measure."
Yet Democratic leaders have balked at the idea.
"We will have a very good, hopefully clean, hard-fought primary that will separate the best nominee out of that pack," said state party chairman John Walsh.
Robert Massie, a former lieutenant governor candidate, is already running. Potential challengers include Setti Warren, the first-term mayor of the affluent Boston suburb of Newton; Kim Driscoll, the mayor of Salem; Rep. Stephen Lynch of South Boston; City Year youth program co-founder Alan Khazei; and Robert Pozen, a businessman.
Capuano and Khazei lost the 2009 Democratic primary to replace Kennedy.
"These are middleweights and lightweights," said Dan Payne, a veteran Boston Democratic strategist. "There is a heavyweight, but it is not clear she will run."
That heavyweight is Elizabeth Warren, a Harvard Law professor tapped by President Barack Obama last year to head the Consumer Financial Protection Bureau. She's been dubbed one of "The New Sheriffs of Wall Street" by Time magazine. But she's given no public signs that she is interested in a Senate run.
Ron Kaufman, a longtime GOP strategist, said there's a chance Patrick could eventually decide to run.
"He'll get a lot of pressure from the White House and national Democrats to run," Kaufman said. "They can't keep control of the Senate if they can't pick up a seat in Massachusetts."
Since his surprising January 2010 special election win, Brown has surprised many Democrats with his political savvy. He was an obscure state senator best known for posing nude for Cosmopolitan magazine and campaigning with his pickup truck and his brown leather "barn coat."
Now he's sitting on more than $7 million in campaign cash. He's got a best-selling autobiography, "Against All Odds: My Life of Hardship, Fast Breaks and Second Chances" and he has emerged in recent polls as one of the most popular politicians in a state long dominated by Democrats.
"People in Massachusetts realize that Senator Brown is as strong as garlic," said Kaufman.
Brown has cast himself as a moderate, seeking to appeal to independents and conservative Democrats. Such support is vital for a Republican to survive in heavily Democratic-leaning Massachusetts. Democrats complain it's all a smokescreen to mask Brown's GOP loyalties.
Democrats were buoyed by how Massachusetts bucked the GOP tide in last fall's midterm elections. The party kept all 10 U.S. House seats and the governorship. Since 2012 is a presidential year, Democrats are hoping Obama's popularity in the state will hurt Brown.
But Marsh said Democrats still need to find a way to unite behind a strong challenger.
"Not to reduce myself to cliches here," she said, "but you can't beat somebody with nobody."