Congressman Joe Kennedy III is joining other Democrats to question President-elect Donald Trump’s legitimacy.

On Tuesday, as he entered a gathering for Massachusetts Democratic activists at Newton South High School, WGBH News asked Kennedy if he believes Trump will be a legitimate president.

“I think there are legitimate questions that are being raised about Russian influence in this election, and exactly what role they played in the election,” Kennedy replied. “I think there needs to be full investigation as to what transpired and who was responsible for it, and whether there were any ties between the Trump campaign and foreign operatives. But until that is — that inquiry has come to a conclusion — the president-elect won, and he's the president-elect.”

Asked again if Trump is a legitimate president-elect, Kennedy answered: “He won the election. That is what it is.”

Last week, Democratic Rep. John Lewis of Georgia told NBC’s Chuck Todd, “I don’t see this president-elect as a legitimate president,” citing his belief that Russian interference helped Trump win the election.

On Martin Luther King Jr. Day, Massachusetts Sen. Elizabeth Warren declined to say whether she agrees with Lewis, who plans to skip Trump’s inauguration. But Warren asserted that Lewis has earned the right to question Trump’s legitimacy.

Despite his concerns, Kennedy plans to attend the Trump inaugural, which he calls a “celebration of … the democratic process.”

Kennedy’s remarks, coupled with Warren’s and Lewis’s, highlight a tricky balance that high-profile Democrats are attempting to strike as Trump takes office. They’re suggesting that his presidency will be compromised from the outset. But in many cases, they’re also urging the Democratic Party to reach out to individuals who voted for Trump and attempt to understand their motivations and concerns.

“The fundamental takeaway of this election for me is the fact that there are an awful lot of people that are hurting across this country that traditionally — the party that has spoken to those people has been the Democratic Party,” Kennedy said. “And … many of those voters decided they trusted Donald Trump more than they did the party they’d normally come home to.

“That has to be a warning call for me, for all the activists here tonight, and for everyone else across our country. And trying to understand where we went wrong and how you build back up that trust and support, that’s our number-one job.”

The meeting Kennedy attended Tuesday was billed by the Massachusetts Democratic Party as a discussion of “the road ahead for Massachusetts Democrats” in the Trump era. But after Kennedy addressed the crowd of some 200, urging them to foster connections with Trump supporters and to make Massachusetts a national showcase for the benefits of progressive policy making, the event grew contentious.

The next speaker, Massachusetts Democratic Party chair Gus Bickford, spoke at length about his plans for helping Democrats retake the governorship in 2018. When Bickford took questions from the audience, many voiced displeasure with the evening’s program. There were complaints that Kennedy left without taking questions, that Kennedy is attending Trump’s inaugural rather than boycotting the event, and that Bickford had focused on the fine points of campaigning without delving into policy.

Afterward, one of the activists in attendance tweeted: “We came to express concerns and organize against Trump, not to be recruited for [get out the vote operations] in 2018.”

I would have said damage exacerbation. We came to express concerns and organize against Trump, not to be recruited for GOTV in 2018.— Alex Borns-Weil (@alexbornsweil) January 18, 2017