U.S. Sen. Elizabeth Warren held on to a strong lead over her two challengers in a new poll out Tuesday, landing 27 points ahead of Republican candidate Geoff Diehl.

In the WBUR/MassINC survey of 506 likely voters, 55 percent said they would vote for the incumbent Democrat Warren, with 28 percent backing Diehl, a state representative from Whitman, and 3 percent behind independent candidate Shiva Ayyadurai. Twelve percent were undecided.

Warren's numbers remained relatively unchanged from the two other WBUR/MassINC polls conducted this year. Diehl's support has grown this year, up from the 20 percent he had in March and 19 percent in May. He originally polled at 32 percent in November 2017, when Warren was at 58 percent.

Including undecided respondents who are leaning toward one candidate, the numbers from this month shifted to 56 percent Warren, 30 percent Diehl, and 5 percent Ayyadurai.

The poll was conducted from Sept. 17-21, via both landline and cellphone. It has a margin of error of 4.4 percent.

A Suffolk University/Boston Globe poll released last week broke the Senate race down similarly, putting Warren ahead of Diehl 54-24, with Ayyadurai at 6 percent.

Warren had nearly $15.6 million in the bank as of Aug. 15 and Ayyadurai had just over $100,000, according to the Federal Election Commission, which did not have campaign finance data available for Diehl.

Thirty-six percent of respondents in the WBUR/MassINC poll said Warren has been too critical of President Donald Trump, while 12 percent said she was not critical enough and 45 percent said she has handled the situation appropriately.

Diehl was a leading surrogate for Trump's campaign in Massachusetts in 2016. He told the News Service earlier this month he has been "willing to call out" the president when he disagrees with his policies, including on Trump's proposal to eliminate state and local tax deductions as part of the Republican tax reform plan.

Fifty-four percent of likely voters polled said they had never heard of Diehl, and 80 percent had never heard of Ayyadurai. Those who had heard of Diehl were split on their opinion of him -- 15 percent viewed him favorably, 14 percent unfavorably, and 17 percent undecided.

Fifty-four percent had a favorable view of Warren, with 39 percent viewing her unfavorably and 6 percent undecided.

Opinions of Warren were divided sharply along party lines. Eighty-one percent of Democrats and 12 percent of Republicans had favorable views of her. Diehl was viewed favorably by 6 percent of Democrats and 34 percent of Republicans.