A strictly partisan effort at this point derided immediately by Trump and other leading Republicans as a sham and a hoax, it is a politically risky undertaking. Democrats say it is their duty, in the aftermath of the Ukraine probe to pursue Trump impeachment, while Republicans say this act will drive Pelosi’s majority from office, AP reported.

Congress must act, Pelosi said. “Democracy is what is at stake.”

“The president’s actions have seriously violated the Constitution,” she said in a somber address at the Capitol. “He is trying to corrupt, once again, the election for his own benefit. The president has engaged in abuse of power, undermining our national security and jeopardizing the integrity of our elections.”

Trump has insisted he did nothing wrong. He tweeted that the Democrats “have gone crazy.”

At the core of the impeachment, the probe is a July phone call with the president of Ukraine, in which Trump pressed the leader to investigate Democrats, including political rival Joe Biden. At the same time, the White House was withholding military aid from Ukraine, an ally bordering Russia.

Drafting articles of impeachment is a milestone moment, only the fourth time in US history, Congress has tried to remove a president, and it intensifies the rigid and polarizing partisanship of the Trump era that is consuming Washington and dividing the nation.

The speaker delivered her historic announcement in solemn tones at the Capitol, drawing on the Constitution and the Founding Fathers in forcefully claiming Congress’ oversight of the president in the nation’s system of checks and balances. Democrats are already beginning to prepare the formal charges, pushing toward House votes, possibly before Christmas.

“Sadly, but with confidence and humility, with allegiance to our founders and a heart full of love for America, today I am asking our chairmen to proceed with articles of impeachment,” Pelosi said.

Seemingly eager to fight, Trump tweeted that if Democrats “are going to impeach me, do it now, fast.” Though he has fought the House investigation, trying to bar current and former officials from testifying, he said he now wants to move on to a “fair trial” in the Senate.

Approval of articles of impeachment is considered likely in the Democratic-majority House. Conviction in a following trial in the Republican-dominated Senate seems very unlikely.