WASHINGTON – U.S. Sen. Tina Smith on Tuesday became the latest Minnesota Democrat to support an impeachment inquiry against President Donald Trump, joining Sen. Amy Klobuchar and a growing number of centrist Democrats in Congress alarmed over reports that he sought Ukrainian help ahead of the 2020 election.

"I support the House beginning impeachment proceedings, as a matter of national security, and protecting the rule of law and our Constitution," Smith said in a prepared statement, moving from her previous position that impeachment talk was premature.

Smith cited recent whistleblower allegations that Trump pressured the Ukrainian government to investigate the role of former Vice President Joe Biden — a leading 2020 challenger — in his son's business dealings overseas.

Smith's statement came amid growing pressure on Democratic leaders to take action against the president in the aftermath of the Special Counsel investigation of Russian meddling in the 2016 election.

Smith's move came a day after two freshman House Democrats from Minnesota, Reps. Angie Craig and Dean Phillips, also threw their weight behind impeachment proceedings. It also puts every Democrat in the Minnesota congressional delegation on record as favoring an impeachment inquiry — with the notable exception of Rep. Collin Peterson, who represents a rural western Minnesota district that voted heavily for Trump.

Peterson, chairman of the House Agriculture Committee, said in his own statement Tuesday that he's not on board with fellow Democrats' calls for an impeachment inquiry over Ukraine.

"If anyone thinks a partisan impeachment process would constrain President Trump, they are fooling themselves," Peterson said. "Without significant bipartisan support, impeachment proceedings will be a lengthy and divisive action with no resolution."

That puts Peterson closer to Minnesota's three Republican congressmen, who are on record opposed to impeaching Trump. Rep. Tom Emmer, who as chairman of the National Republican Congressional Committee is leading the effort to break the Democrats' House majority, said Tuesday that impeachment would hurt House Democrats politically.

Democrats "have become so radicalized by their hatred of President Trump that they are willing to plunge the nation into a constitutional crisis based on secondhand gossip," Emmer said in a statement. "Make no mistake about it: backing impeachment will cost the Democrats their majority in 2020."

Smith, facing re-election in 2020, immediately came under fire from GOP challenger Jason Lewis, who accused her of rushing to judgment without evidence. "Tina Smith and the Democratic Party have demonstrated time and again that they are all too willing to make a mockery of our Constitution by rushing to judgment and shredding due process in order to score cheap political points with their radical, angry political base," Lewis said.

After days of relative silence, Republicans in Congress began a political counteroffensive in recent days, questioning the reports of the anonymous whistleblower said to have direct knowledge of Trump's conversation with Ukrainian President Volodymyr Zelensky last July. Trump also signaled Tuesday that he was preparing to release a transcript of the disputed call, which his aides said would quell the Democrats' criticism.

Klobuchar, a candidate for president, called on the White House to make available the whistleblower's entire report, not only the call transcript.

"Remember it's the whistleblower complaint we must see," Klobuchar wrote on Twitter. "Not just one call. Complaint reportedly involves more. It isn't legal to sell out your country for personal gain."

Impeachment proceedings appeared imminent on Tuesday with House Speaker Nancy Pelosi announcing a formal impeachment inquiry, a dramatic reversal for the Democratic leader who had previously advocated a more measured approach.

Trump's interactions with Ukraine allegedly involved his insistence that the country investigate business dealings there of Hunter Biden, Joe Biden's son. Trump's 2016 campaign chairman, Paul Manafort, was previously prosecuted over his own lobbying work in Ukraine.

On Tuesday, the Washington Post reported that the Justice Department has closed its investigation into work on behalf of Ukrainian interests by Manafort's one-time associate, Vin Weber, a once-powerful D.C. lobbyist and a former Republican congressman from Minnesota.

An attorney for Weber told the Post that "at all times Mr. Weber acted in good faith and in keeping with the legal advice his company received from the outset."

Patrick Condon • 202-662-7452