The U.S. House of Representatives is launching an impeachment inquiry of Donald Trump over allegations he tried to press a foreign government into helping him take down a political rival, the first formal step in removing the President from power before the 2020 election.

Speaker Nancy Pelosi accused Mr. Trump of a “betrayal of his oath of office” as she announced the Democrat-controlled House would make the first move toward impeachment.

Mr. Trump is accused of trying to ransom US$400-million in military aid in a bid to push Ukrainian President Volodymyr Zelensky to investigate Joe Biden, the former vice-president, who is a leading contender for the Democratic presidential nomination, over the Ukrainian business dealings of his son, Hunter Biden.

“The actions taken to date by the President have seriously violated the Constitution,” Ms. Pelosi said Tuesday afternoon after a Capitol Hill caucus meeting.

Democrat-led House committees have been investigating Mr. Trump for months. Ms. Pelosi said their probes would now fall under an “umbrella of impeachment inquiry,” making it increasingly likely that the investigations would lead to articles of impeachment against the President. The committees are now gathering information to inform those articles of impeachment.

If the Democrat-majority House approved one or more articles of impeachment, Mr. Trump would face a trial before the Republican-led Senate. It would then take a two-thirds vote of the Senate to push him out of office.

The proceedings could also logjam congressional action on other major files, including attempts to ratify Mr. Trump’s United States-Mexico-Canada Agreement that is meant to replace NAFTA.

Mr. Trump, in a bid to calm the gathering storm, said Tuesday that he would release a transcript of a July 25 telephone call he had with Mr. Zelensky, in which he is believed to have pressed for the investigation of Joe Biden.

But Ms. Pelosi signalled this would not be enough: The Democrats want the Trump administration to also stop blocking the release of a whistle-blower complaint about the matter that is believed to contain more extensive information than the single phone call. And Adam Schiff, chairman of the House intelligence committee, said he was in talks with the whistle-blower’s lawyer to have the tipster meet privately with a legislative committee later this week.

The White House is mulling releasing the whistle-blower complaint, as well as a report into the matter by intelligence community inspector-general Michael Atkinson, Politico reported late Tuesday, citing unnamed officials.

The President took to Twitter to accuse Ms. Pelosi of trying to “ruin” his day at the United Nations General Assembly with her announcement. “PRESIDENTIAL HARASSMENT!” he wrote.

Mr. Trump has offered shifting explanations in recent days for his actions on Ukraine. Speaking with reporters Tuesday morning, he simultaneously denied pushing Ukraine to investigate Mr. Biden and called on the country to do exactly that.

“Even the Ukrainian government put out a statement that that was a perfect call. There was no pressure put on them whatsoever,” he said. “But there was pressure put on with respect to Joe Biden. What Joe Biden did for his son, that’s something they should be looking at.”

The President also seemingly confirmed reports by The Washington Post and The New York Times that he tried to stop nearly US$400-million in help to Ukraine’s military, which is battling Russian-backed forces in the country’s east, shortly before he spoke with Mr. Zelensky. Mr. Trump said Monday he tried to block the funds because Ukraine is a corrupt country. But on Tuesday, he gave a different reason, saying he had actually attempted to stop the money from flowing because he felt European countries should take more responsibility for Ukraine’s defence.

In a speech in his home state of Delaware, Mr. Biden accused Mr. Trump of committing an “abuse of power” and “shredding the United States Constitution.”

“Pressuring the leader of another nation to investigate a political opponent, to help win his election, is not the conduct of an American President,” he said. “Denying Congress the information to which it is constitutionally entitled, and obstructing its efforts to investigate his actions, is not the conduct of an American President.”

Ms. Pelosi has for months resisted calls from some members of her caucus to back the impeachment of Mr. Trump over accusations that his presidential campaign co-operated with Russian efforts to tip the 2016 election in his favour, then tried to cover it up. The Speaker and other moderate Democrats have argued that impeachment will take time, divert attention away from more popular moves on policy issues such as health care, alienate centrist voters who do not care about impeachment and rile up the President’s base.

But the rapidly unspooling Ukraine scandal has suddenly changed her approach and united the Democrats’ fractious caucus in calling for tougher action to hold Mr. Trump to account.

The matter only came to light two weeks ago when the acting director of national intelligence, Joseph Maguire, refused to allow Mr. Atkinson to disclose the substance of the whistle-blower complaint or the results of his investigation to Congress.

Saikrishna Prakash, an expert in constitutional law and impeachment, pointed out that Ms. Pelosi’s carefully worded statement stopped short of actually backing articles of impeachment, leaving her room to manoeuvre. For Ms. Pelosi, whether to impeach is a more political than legal calculation, he said.

“She’s said something to placate her base but without committing herself to bring an impeachment motion to a vote,” said Prof. Prakash of the University of Virginia’s Miller Center. “I think she’s holding on to all her options.”

Adrian Morrow
U.S. Correspondent
The Globe and Mail, September 24, 2019