WASHINGTON — The White House's open defiance of the impeachment investigation has thrown the process into turmoil, with Donald Trump's loyalists and adversaries scrambling to carve a path forward in the battle over the American presidency.
While some believe House Speaker Nancy Pelosi's effort to hold Trump accountable is a profile in constitutional courage, Trump loyalists see a hyper-partisan abuse of power.
Either way, the process is likely to provoke a "national nightmare," as constitutional scholar Cass Sunstein put it in his 2017 book "Impeachment: A Citizen's Guide."
Will Democrats succeed in obtaining documents and testimony from key witnesses such as US diplomats, whose text messages show they helped coordinate efforts to pressure Ukraine into investigating Trump's political adversary Joe Biden?
Or can Trump thwart the process and essentially block congressional oversight?
Impeachment proceedings have been undertaken just three times before in America's 243-year history.
Andrew Johnson and Bill Clinton were impeached by the House of Representatives but survived Senate trials, while Richard Nixon, facing almost certain impeachment and conviction by the Senate, resigned in 1974.
Today's crisis "is a historic showdown," Chris Edelson, an assistant professor of government at American University, told AFP.
The focus of the current impeachment investigation -- pressuring another country's leader to interfere in US elections -- "is certainly a first," he said, decrying Trump's "brazen" effort with Ukraine.
The White House and its defenders have seized on Pelosi's refusal to hold a floor vote to launch the inquiry, arguing the entire process is illegitimate.
Law professor Frank Bowman at the University of Missouri disagrees.
"Nothing in the House rules requires that a resolution be passed before the full House... can take steps to exercise impeachment power," Bowman wrote in a blog post.
Pelosi has not signaled her timeline for filing articles of impeachment, but lawmakers predict it could happen this year.
Several House committees are gathering information as part of the probe, and while they have been blocked at multiple turns, Pelosi says there is a "growing body of evidence" that shows Trump abused his office.
As the process accelerates, Trump's administration is girding for war in the courts, and a case Tuesday in Washington related to special counsel Robert Mueller's Russia investigation may prove instructive.
In arguing to a judge that House requests for grand jury materials in the Mueller probe be denied, Justice Department lawyers pointed to Nixon's impeachment case and said courts should not have given Watergate grand jury data to Congress, The Washington Post reported.
Nixon went to the Supreme Court in his failed bid to prevent the release of incriminating White House tapes, so there is potential for the high court to be drawn into today's impeachment fight.
Trump said as much Wednesday: "It probably ends up being a big Supreme Court case," he told reporters.
Democrats are mulling whether to engage in a protracted court battle, or wrap up their investigation with the evidence they have, add White House obstruction to articles of impeachment, and pull the trigger.
"The 3-year and still ongoing efforts to gain access to President Trump's federal income tax returns perfectly illustrate how effective" a White House legal team can be at stalling judicial proceedings, Harvard Law School constitutional scholar Laurence Tribe wrote in Wednesday's USA Today.
If Trump is impeached, the process shifts to the Senate for a trial, where he can defend himself before the chamber.
To date, few Senate Republicans have expressed deep concerns about Trump's behavior. With two-thirds of senators needed for a conviction, and Republicans in control 53-47, the odds remain in the president's favor.
POLITICAL BATTLE AHEAD
With the crisis intensifying months before the first votes in the Democratic nomination process, beginning February in Iowa, will voters want the presidential race consumed by impeachment?
Americans are increasingly supportive of an inquiry, with about half of voters now in favor, recent polling shows.
But Democrats could turn hesitant about pursuing an ouster of Trump through any means other than the election if the process gets pushed too far into 2020.
"Obviously, the public forms an opinion over time as to the seriousness of the charges," Elaine Kamarck, director of the Brookings Institution's Center for Effective Public Management, wrote of previous impeachment efforts. "And they will do so again."
© Agence France-Presse