Lawmakers set to weigh impeachment charges in Congress against Donald Trump

The next phase of impeachment begins Wednesday in the US Congress as lawmakers weigh charges against Donald Trump, after the high-stakes inquiry into the president detailed "overwhelming" evidence of abuse of power and obstruction.

Four constitutional scholars will testify before the House Judiciary Committee in the first of a series of hearings to establish the gravity of Trump's alleged crimes.

On Tuesday, congressional Democrats made a forceful case that Trump should be removed from office for abusing his powers by pressuring Ukraine for dirt on a Democratic election rival.

"The president placed his personal political interests above the national interests of the United States, sought to undermine the integrity of the US presidential election process and endangered US national security," said the final report on the House Intelligence Committee's probe, led by lawmaker Adam Schiff.

"President Trump and his senior officials may see nothing wrong with using the power of the office of the president to pressure a foreign country to help the president's reelection campaign," it said.

"However, the Founding Fathers prescribed a remedy for a chief executive who places his personal interests above those of the country: impeachment."

The report is expected to form the basis for the Judiciary Committee to draw up formal charges -- articles of impeachment -- that could include bribery, abuse of power, obstruction and contempt of Congress.

Democrats reportedly aim to have the articles presented for a vote to the entire House of Representatives before Christmas on December 25.

If they pass as expected, Trump would then stand trial for removal in the Republican-controlled Senate, where he is expected to be exonerated. On Tuesday, White House spokeswoman Stephanie Grisham dismissed both the report and the impeachment process.

"At the end of a one-sided sham process, Chairman Schiff and the Democrats utterly failed to produce any evidence of wrongdoing by President Trump," she said in a statement.

The report mapped out a months-long scheme by Trump, his personal lawyer Rudy Giuliani and senior diplomats and White House staffers to pressure Ukraine's president into investigating Joe Biden, the current favorite to win the Democratic White House nomination in 2020.

Trump also pressured President Volodymyr Zelensky to investigate a "conspiracy theory" that it was Ukraine -- not Russia -- that interfered in the 2016 US election, to benefit the Democrats.

In both cases, the report said, Trump conditioned nearly $400 million in US military aid and a high-profile summit with Zelensky on Kiev opening the investigations, which Democrats have said amounts to bribery.

The report also makes a strong case for charges of obstruction against Trump, for refusing to provide documents to investigators, preventing witnesses from appearing and threatening some of those who did appear.

To counter Republican attacks on the impeachment process, Judiciary Committee chair Jerry Nadler has invited a mix of liberal and conservative constitutional scholars to testify Wednesday.

They include Noah Feldman of Harvard Law School, Pamela Karlan of Stanford Law School, Jonathan Turley of The George Washington University Law School and Michael Gerhardt from The University of North Carolina School of Law.

Turley, a conservative, has called Trump's behavior inappropriate but said Democrats need much more evidence to prove their case.

"Abuse of power is impeachable, but it is the most difficult of potential impeachment claims," he wrote on his website.

"If Democrats continue with their plan to impeach Trump by the end of December, they would be presenting the thinnest record and fastest impeachment investigation in history." Gerhardt told Slate that the allegations against the president appear impeachable.

However, he said, whatever the Constitution says, politics and public opinion are involved, especially with an election coming up next year.

The authors of the Constitution "thought that the American people would care about facts, the American people would largely become educated, and they would care about the Constitution," he said.

"And it's not entirely clear that they do.