Rep. Stephen Lynch said Wednesday he’s concerned that pursuing an impeachment inquiry against President Donald Trump could hurt Democrats in the 2020 election.

“I do think if we handle this poorly, it could backfire,” Lynch told Greater Boston host Jim Braude.

But Lynch said that the president’s July phone call to the president of Ukraine, in which Trump allegedly threatened to withhold military aid to Ukraine unless officials investigated the son of his political rival former Vice President Joe Biden, left him “no choice.”

“I really have no choice at this point. [Trump] was trying to get a foreign country to undermine our democratic process in our election,” Lynch said.

“We can’t let this continue. ... If we’re going to defend the constitution, we’re going to have to step up,” he added.

Lynch also addressed Rep. Joe Kennedy’s 2020 primary challenge to Sen. Ed Markey. Kennedy announced his bid in September.

Lynch endorsed Markey before Kennedy got into the race, and said he would keep his promise.

“I gave my word,” he said.

However, Lynch suggested that — had he waited until Kennedy entered the race — he wouldn't have endorsed anyone at all.

“I would’ve taken a walk. I wouldn’t get into a fight between my two friends, my two colleagues,” he said.

Lynch also faces a primary challenge in 2020, from video game designer Brianna Wu, who ran against him previously in 2018.