WASHINGTON — Assistant House Speaker Ben Ray Lujan of New Mexico on Monday became the highest ranking House Democrat to call for opening an impeachment inquiry into President Donald Trump.

“I support moving forward with an impeachment inquiry, which will continue to uncover the facts for the American people and hold this president accountable," Lujan, the fourth-ranking Democrat in the House, said in a statement. “This is not a position I've reached lightly."

Lujan, who is running for the Senate in 2020, cited the findings of the Mueller report and Trump's lack of action on election security: “What is evident is that President Trump is abdicating his responsibility to defend our nation from Russian attacks and is putting his own personal and political interests ahead of the American people.”

Lujan’s announcement comes despite Speaker Nancy Pelosi's repeated calls for her caucus to focus their attention on congressional investigations and ongoing legal battles instead of impeachment.

Rep. Katherine Clark of Massachusetts, the sixth-ranking House Democrat as vice chair of the Democratic Caucus, had been the highest-ranking Democrat to back an inquiry.

An NBC News tally of Democrats calling for an impeachment inquiry has reached 125, more than a majority of the party's caucus. One independent member of Congress, Rep. Justin Amash of Michigan, has also voiced support.

The chairman of the House Judiciary Committee, Rep. Jerry Nadler, D-N.Y., has said that his committee is investigating whether to recommend articles of impeachment against Trump to the House, and has indicated it could make that determination by the late fall.