By LISA MASCARO, MARY CLARE JALONICK and JULIE PACE Associated Press

WASHINGTON (AP) — Washington plunged into an impeachment crisis on Wednesday, as House Democrats opened an investigation into President Donald Trump's campaign season dealings with Ukraine. Trump repeatedly prodded Ukraine's president to look into Democratic rival Joe Biden, according to a rough transcript released by the White House.

"Whatever you can do with the attorney general would be great," Trump said in the summer phone call. He was referring to Attorney General William Barr, the nation's top law enforcement official.

The president's words set the parameters of the political debate to come, with saying that it laid the predicate for an impeachment inquiry and Trump dismissing it as a "nothing call."

The release came against the backdrop of Trump's meetings with world leaders at the United Nations, a remarkable split screen even for the turbulence of the Trump era. On Trump's schedule Wednesday: a meeting with Ukrainian President Volodymyr Zelensky, whose contacts with Trump are now central to the impeachment inquiry.

House Speaker Nancy Pelosi launched the formal impeachment inquiry on Tuesday, yielding to mounting pressure from fellow Democrats and plunging a deeply divided nation into an election year clash between Congress and the commander in chief. The probe injects deep uncertainty into the 2020 election campaign and tests anew the nation's constitutional system of checks and balances.

Trump, who thrives on combat, has all but dared Democrats to take this step, confident that the specter of impeachment led by the opposition party will bolster rather than diminish his political support.

"Just so you understand, it's the single greatest witch hunt in American history, probably in history," Trump said during a meeting with foreign leaders in New York.

While Pelosi's announcement adds weight to the work being done on the oversight committees, the next steps are likely to resemble the past several months of hearings and legal battles — except with the possibility of actual impeachment votes.

Her brief statement, delivered without dramatic flourish but in the framework of a constitutional crisis, capped a frenetic weeklong stretch on Capitol Hill as details of a classified whistleblower complaint about Trump burst into the open and momentum shifted toward an impeachment probe.

For months, the Democratic leader has tried calming the push for impeachment, saying the House must investigate the facts and let the public decide. The new drive was led by a group of moderate Democratic lawmakers from political swing districts, many of them with national security backgrounds and serving in Congress for the first time. The freshmen, who largely represent districts previously held by Republicans where Trump is popular, risk their own reelections but say they could no longer stand idle. Amplifying their call were longtime leaders, including Rep. John Lewis of Georgia, the civil rights icon often considered the conscience of House Democrats.

"Now is the time to act," said Lewis, in an address to the House. "To delay or to do otherwise would betray the foundation of our democracy."

At issue are Trump's actions with Ukraine. In a summer phone call with Zelenskiy, he asked for help investigating former Biden and his son Hunter. In the days before the call, Trump ordered advisers to freeze $400 million in military aid for Ukraine — prompting speculation that he was holding out the money as leverage for information on the Bidens. Trump has denied that charge, but acknowledged he blocked the funds, later released.

Biden said Tuesday, before Pelosi's announcement, that if Trump doesn't cooperate with lawmakers' demands for documents and testimony in its investigations the president "will leave Congress ... with no choice but to initiate impeachment." He said that would be a tragedy of Trump's "own making."

The Trump-Ukraine phone call is part of a whistleblower's complaint, though the administration has blocked Congress from getting other details of the report, citing presidential privilege.

The whistleblower's complaint was being reviewed for classified material and could go to Congress by Thursday, according to a person familiar with the issue who was not authorized to discuss it publicly and spoke on condition of anonymity.

Trump has sought to implicate Biden and his son in the kind of corruption that has long plagued Ukraine. Hunter Biden served on the board of a Ukrainian gas company at the same time his father was leading the Obama administration's diplomatic dealings with Kyiv. Though the timing raised concerns among anti-corruption advocates, there has been no evidence of wrongdoing by either the former vice president or his son.

While the possibility of impeachment has hung over Trump for many months, the likelihood of a probe had faded after special counsel Robert Mueller's Trump-Russia investigation ended without a clear directive for lawmakers.

Since then, the House committees have revisited aspects of the Mueller probe while also launching new inquiries into Trump's businesses and various administration scandals that all seemed likely to drag on for months.

But details of Trump's dealings with Ukraine prompted Democrats to quickly shift course. By the time Pelosi addressed the nation Tuesday, about two-thirds of House Democrats had announced moving toward impeachment probes.

The burden will probably now shift to Democrats to make the case to a scandal-weary public. In a highly polarized Congress, an impeachment inquiry could simply showcase how clearly two sides can disagree when shown the same evidence rather than approach consensus.

On Wednesday, the Democratic-controlled House is expected to consider a symbolic but still notable resolution insisting the Trump administration turn over to Congress the whistleblower's complaint. The Republican-led Senate, in a rare bipartisan moment, unanimously approved a similar resolution Tuesday.

The lawyer for the whistleblower, who is still anonymous, released a statement saying he had asked Trump's director of national intelligence to turn over the complaint to House committees and asking guidance to permit the whistleblower to meet with lawmakers.

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Associated Press writers Michael Balsamo, Laurie Kellman, Andrew Taylor, Eric Tucker and Zeke Miller in Washington and Jonathan Lemire and Deb Riechmann in New York contributed to this report.

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