As Elizabeth Warren climbs in the polls, Joe Biden’s Massachusetts allies are warning that her election history suggests she runs weakest among the types of voters Democrats need to win over to capture the White House.

While Warren won reelection easily in 2018, Biden’s backers point to her performance among independent and blue-collar voters as evidence she’ll fail to appeal to similar voters in the Rust Belt — just as Hillary Clinton did in 2016.

“The grave concern of many of us Democrats in Massachusetts is that in many of the counties where Sen. Warren underperforms, they are demographically and culturally similar to voters in key swing states,” said state Rep. John Rogers, who backs Biden.

“The tangible fear here,” Rogers said, “is that these Massachusetts counties are bellwethers for states like Pennsylvania, Wisconsin, Michigan, Ohio — key states that Democrats can't afford to lose in the battle to beat President Trump.”

Warren’s critics have long assailed the former Harvard Law School professor for being too far liberal and too out-of-touch with blue-collar voters to beat Donald Trump, despite an economic message that speaks directly to many of their concerns. Electability, meanwhile, is the core of Biden’s argument for the nomination: his campaign frames him as the Democrat best positioned to defeat Trump.

Skeptics of Warren’s "electability" typically haven’t hailed from Massachusetts, where in 2018 she handily defeated Republican Geoff Diehl, who embraced Trump in a state where the president is wildly unpopular. Yet even in victory — which she achieved without buying any television ads — Warren’s 60 percent to 36 percent winning margin failed to impress: She lagged behind the four other Democrats who won statewide office that year.

While Warren racked up large margins in Boston and other liberal bastions, she won only half of the 20 towns with the most independent voters.

State Rep. Angelo M. Scaccia pointed out even Gov. Charlie Baker — the lone Republican to win last year in the solidly blue state — received a higher percentage of the vote than Warren in 2018, as well as more total votes.

“The Republican governor was the top vote-getter, and the secretary of state got more votes than Warren, outscored her very badly,” said Scaccia, a moderate Democrat. He said Warren should’ve “crushed” Diehl by a larger margin considering he was running as a proud Trump Republican in Massachusetts.

“It was the year of the woman,” Scaccia said. “She should’ve done much better.”

Scaccia noted that Warren also ran well behind Massachusetts Attorney General Maura Healey, another woman running statewide for reelection in 2018. Healey, who won 70 percent of the vote statewide, captured a higher share of the vote than Warren in 337 of the state’s 351 towns and cities.

Another Democratic member of the Massachusetts Legislature who supports Biden but who did not want to go on record criticizing Warren, said the senator’s performance in the state was reminiscent of Clinton’s struggles against Trump in 2016 among non-college-educated and white suburban voters.

“A vote for Elizabeth Warren in the primary is a vote for Trump in the general,” the self-described progressive Democrat said. “We’re thinking about the swing voters in other states, and we don’t want a repeat of what happened last time.”

Some national and state polls have found Biden running stronger against Trump than Warren, in part because of his appeal with independent voters. A recent Marquette University survey in swing-state Wisconsin, for instance, showed Biden beating Trump by 9 percentage points while Warren tied him at 45 percent each. With independent voters in the poll, Biden leads Trump by 22 points while Warren trails him by 8.

And a new ABC/Washington Post poll found that 42 percent of Democrats nationally think Biden would fare best against Trump, 14 percent said Vermont Sen. Bernie Sanders and 12 percent said Warren. In head-to-head matchups, Biden beats Trump by 15 points and Warren beats him by 7 in the poll, which shows Biden head of the president by 14 points among independents while Warren is up by only 4.

Non-college-educated voters — who strongly favored Trump in 2016 — favor Biden by 6 points while Warren ties Trump with this group, the poll shows.

Warren’s supporters accuse Biden’s Massachusetts backers of cherry-picking data as the polls begin to show her gaining traction. While the senator’s campaign declined to comment for this story, it referred to a postelection analysis authored by state Democratic Party Chairman Gus Bickford, who lauded her win as “the greatest margin of victory of any Democratic Senate or Gubernatorial candidate in Massachusetts in the last 10 years.”

According to Bickford’s analysis, Warren also improved her standing with rural voters and in nonwhite communities.

State Sen. Eric Lesser, a Warren supporter, said Warren is gaining ground with independently minded voters in his Springfield-based district, which has a mix of rural and suburban voters where five of the nine communities voted for Trump.

“My district was home to dozens of huge manufacturing centers,” he said, ticking off the companies that closed and moved out. “They left in the '70s and '80s, and people in my community are looking for someone for an answer to that. And Elizabeth Warren and her message connects with them.”

Mary Anne Marsh, a senior adviser to former Massachusetts Sen. John Kerry, said the criticisms coming from Biden’s supporters make them sound “very nervous.”

“I've heard this as part of conventional wisdom, just like I’ve heard Joe Biden can beat Trump. But since April [when he announced his candidacy], he’s been terrible,” she said. “What, third time’s the charm? He has run for president twice before. What makes people think this time will be any different?”

As for Warren’s blue-collar appeal, Marsh pointed out that Warren beat incumbent GOP Sen. Scott Brown 54-46 percent in 2012 — and did it with the support of the firefighters’ union that has, in her estimation, too often sided with Republicans.

Scott Ferson, a political consultant who is neutral in the race, said Warren reminds him of his old boss, the late Sen. Ted Kennedy, who was perceived as too liberal in less urban parts of the state.

“Elizabeth Warren can be polarizing a little bit, what some see as stridency, in more conservative sections of the state, which is Kennedy-esque,” he said. “But she beat Scott Brown, and he drove a pickup truck. I get the concern, but I think these legislators may be a little too sensitive.”