But Joseph Ricca, a seasoned Democratic operative with extensive state and national campaign experience, said the hand-wringing by Democratic party insiders over Warren’s prospects is probably misplaced.

Analysts say that shift could well have been connected to Brown’s rise in the recent poll numbers. Along with a campaign war chest that is twice as large as his challenger’s - Brown had amassed nearly $13 million by the end of 2011, to Warren’s $6.1 million - the poll numbers also make it difficult for Brown to continue to paint himself as the underdog, as he has done since Warren entered the race.

Brown has relied on a strategy of distancing himself from national Republicans, whose positions often prove too conservative for Massachusetts voters. That marks a pivot from when he was something of a darling of the conservative right and the Tea Party movement, leading up to his special election victory in January 2010.

“She has come out of the starting gate incredibly fast, but since then she has plateaued,’’ he said. “The burst of good feeling that greeted her candidacy has worn off.’’

“Elizabeth Warren has to show she has a second act,’’ said Dan Payne, a Democratic media analyst. Payne said his conversations with Democratic leaders have suggested that there is some degree of concern.

As the mood of the electorate appears to have swung toward the incumbent senator, it has shaken much of the early confidence among the Democrats who, thrilled with the energy that went into her first months of Warren’s campaign, were convinced that she would beat Brown in November.

In a handful of previous polls, Warren had led Brown, or come within the margin of error, while Brown’s favorability ratings appeared to be slipping.

A new poll released over the weekend by the Western New England University Polling Institute in partnership with The Republican newspaper of Springfield found Brown leading Warren, his top Democratic challenger, 49 to 41 percent. That closely reflects several other surveys taken in the last month that also show Brown with a lead.

The campaign’s reshaped landscape, which appears to have shifted in Brown’s favor, has created a quiet buzz among some in the party that Warren, despite her incredible burst onto the Massachusetts electoral map last fall, has hit some strong headwinds and will need to recapture the excitement that lit up the Bay State’s political world when she entered the race in September.

After a huge rush of optimism that Elizabeth Warren’s candidacy would end Scott Brown’s hold on his US Senate seat, Democratic insiders and activists are awakening to a new political reality, driven by a series of recent polls and Brown’s success these past few months in crafting an independent bipartisan image.

“I hear that talk from some prominent Democrats,’’ Ricca said. However, Warren, who began the race without any electoral experience, has proven that she has the skills and message to carry the day for the Democrats this fall, he said.

“She has gone from a political unknown to a serious challenger to Brown, a popular political figure, in seven months,’’ Ricca added. “That absolutely incredible.’’

Warren aides, too, say the concerns are unwarranted, noting that the election is still eight months away and that in the run up to Election Day, her message of economic inequality and the middle-class squeeze will trump Brown.

“Elizabeth is focused on meeting voters across the state and talking about the economic issues that are affecting middle-class families,’’ said Doug Rubin, Warren’s senior advisor. “The polls have been up and down throughout the race, but it’s very early and the campaign is focused on building a strong, statewide grass-roots organization. That’s how Democratic candidates win in Massachusetts.’’

The Warren campaign has also taken issue with Brown’s attempts to paint himself as an independent voice.

Indeed, Brown has wandered off the GOP reservation enough to claim some independence, but he has also toed a strong partisan line on a number of key issues: opposing President Obama’s health care bill, cosponsoring a proposal to allow employers to deny certain health care coverage on moral grounds, and opposing any tax increases, even on the wealthy.

But, if several of the recent polls are correct, Brown may have benefited from his positions on social issues in the last few weeks, such as the one over whether Catholic institutions should be forced to provide contraception in their health care plans for workers.

That has meant that the discussion has not focused on her economic message, which Democratic analysts feel is Warren’s best bet to beat Brown.

“Recently, issues that have been raised - whether to provide contraception as part of the health care reform and whether women should serve in the front lines of combat - have been on Brown’s turf,’’ Payne said.

He emphasized that Warren must now redirect the conversation to her own economic message.

Maurice T. Cunningham, the chairman of the political science department at the University of Massachusetts Boston, said he thinks the party insiders must take the long view, noting that much will happen between now and November that will shape the race.

“They need to come off the ledge and put the sharp instruments away,’’ Cunningham said. “A year ago, they couldn’t conceive of beating Scott Brown, but now they are despondent because she is four to nine points behind him. That makes no sense.’’

Brown also got an unexpected boost last week when Senator Olympia Snowe, the moderate GOP from Maine, shocked political observers with her announcement that she was retiring because of her frustration with the hyperpartisanship in Washington.

Snowe’s retirement gives a strong voice to Brown’s argument that Washington needs moderates within the Republican ranks.

Asked Friday about Snowe’s decision, Brown reiterated that point. “I think it’s even more important to have me back there because I’m the guy that’s working across the aisle on a regular basis,’’ he said.

Noah Bierman of the Globe staff contributed to this report. Frank Phillips can be reached at phillips@globe.com. Follow him on Twitter @GlobeFPhillips.

© Copyright 2012 Globe Newspaper Company.