Leading Democratic presidential candidates were nearly unanimous in backing impeachment proceedings against President Donald Trump after he tried to get Ukraine to investigate a political rival, former Vice President Joe Biden.

“I said it on the floor of the US Senate in May & I’ll say it again: Congress must fulfill its Constitutional duty & begin impeachment proceedings against the President,” Massachusetts Sen. Elizabeth Warren said on Twitter. “Nobody is above the law — not even the President of the United States.”

Speaker Nancy Pelosi, D-Calif., announced Tuesday that the House will open an impeachment inquiry over Trump’s solicitation of a Ukrainian corruption investigation targeting Biden, a leading contender for the 2020 Democratic presidential nomination.

Trump froze millions of dollars in congressionally approved aid to Ukraine a few days before a phone call to President Volodymyr Zelensky in which he raised unsubstantiated allegations against Biden and the former vice president’s son, Hunter, who did business there. Trump has confirmed that he spoke to the Ukrainian president about the Bidens; he also acknowledged that he held up aid for Ukraine’s fight against Russia-backed separatist rebels, but said he did so because he thought European allies were not contributing enough.

Sen. Bernie Sanders of Vermont agreed with Warren, saying the president may have “used funds designed to protect the security of the United States as a means to gain political dirt on an opponent.”

Sen. Cory Booker of New Jersey said Congress must act against a president who fails to respect the checks and balances of government. He dismissed concerns among Democrats that impeachment could backfire by generating public sympathy for Trump.

“What we’re facing isn’t a political issue, it’s a moral one,” he said in a statement. “In 2016, Trump openly welcomed foreign adversaries to meddle in our democracy for his own political gain. Now, by his own admission, he appears to be using the same playbook to undermine our democratic institutions and remain in power.”

Many of the Democrats running for the party’s 2020 presidential nomination had already called for Trump’s impeachment over alleged obstruction of justice in the investigation of Russian interference in the 2016 U.S. presidential election.

One of them, Sen. Kamala Harris of California, said Trump’s solicitation of Ukraine’s assistance for his reelection campaign provided a new reason to start the impeachment process.

“Donald Trump has abused his power, obstructed justice, and violated his oath of office,” Harris said on Twitter. “He puts his political interests over our national interest. I agree with @SpeakerPelosi — no one is above the law. He must be impeached.”

Biden said Tuesday that Trump should be impeached if he fails to cooperate with House investigators.

Candidate Pete Buttigieg, mayor of South Bend, Ind., told MSNBC that Trump had “made it clear that he deserves to be impeached,” saying the president’s admitted request for a Ukrainian investigation of Biden was “shocking.”

“I support the House in taking on impeachment proceedings,” he said. “I also think the only real resolution to this will be defeating the president and his enablers in the congressional Republican caucuses. Look, what’s going on here is shocking. The president of the United States confessed to official misconduct.”

Sen. Amy Klobuchar of Minnesota, former U.S. Housing Secretary Julian Castro, New York businessman Andrew Yang, San Francisco billionaire Tom Steyer and others joined their Democratic rivals in welcoming the impeachment investigation.

Fighting the tide was Rep. Tulsi Gabbard of Hawaii, who has scored relatively low in polls of Democrats competing for the nomination.

“I’ve been consistent in saying that I believe that impeachment at this juncture would be terribly divisive for the country,” Gabbard told Fox News on Tuesday.

Montana Gov. Steve Bullock, another Democrat struggling to gain traction in the presidential race, called on Congress on Tuesday to demand a whistleblower’s complaint about Trump’s conduct, along with transcripts of Trump’s interactions with Ukrainians.
“If they don’t get it,” he said, “I see no other option than starting impeachment proceedings.”

The acting director of national intelligence, Joseph Maguire, has refused to share details of the complaint with lawmakers, citing presidential privilege. Trump tweeted Tuesday that he would release a transcript of his call with Zelensky.

Former Rep. Beto O’Rourke of Texas said there was no need for transcripts.

“The president admitted to asking a foreign power to investigate a political opponent,” O’Rourke said on Twitter. “Impeach him.”

One of Trump’s Republican challengers, former Massachusetts Gov. Bill Weld, suggested Trump’s efforts with Ukraine had betrayed the United States.

“It’s treason pure and simple, and the penalty for treason under the U.S. code is death,” Weld told MSNBC. If the Senate convicts a president after impeachment by the House, he said, the penalty “is removal from office, and that might look like a pretty good alternative to the president if he could work out a plea deal.”