Members of the U.S. Senate will spend Wednesday asking their questions about the issues involved in the impeachment of President Donald Trump, after spending parts of six days listening to a group of lawmakers from the House of Representatives make a case for convicting the president and his lawyers arguing he did nothing wrong.

Senate Republicans and Democrats will alternate submitting their written questions to be read by Chief Justice John Roberts. The questions can be directed at either the House members serving as prosecutors or Trump’s legal team, and there is no set time limit for their responses.

The process will continue Thursday, before the chamber proceeds to considering whether they will vote to allow witnesses in the trial.

U.S. Senate Majority Leader Mitch McConnell arrives at the U.S. Capitol for the Senate impeachment trial of President Donald Trump in Washington, Jan. 28, 2020.

Calling witnesses

Senate Majority Leader Mitch McConnell told fellow Republicans Tuesday that he did not have enough support among the Republican majority to stop Democrats from calling witnesses.

McConnell and the president’s defense team oppose calling witnesses, including former national security adviser John Bolton who claims in an upcoming book that Trump directly told him that he was withholding military aid to Ukraine in exchange for a political favor.

Trump tweeted late Tuesday reiterating his objections.

No matter how many witnesses you give the Democrats, no matter how much information is given, like the quickly produced Transcripts, it will NEVER be enough for them. They will always scream UNFAIR. The Impeachment Hoax is just another political CON JOB!

— Donald J. Trump (@realDonaldTrump) January 29, 2020

Fifty-one of the 100 senators hearing the impeachment case would have to vote in favor of witnesses, meaning four Republicans would have to side with the 47 Democrats and independents.

Several moderate Republicans, including Mitt Romney, Susan Collins and Lisa Murkowski, have said they may be interested in hearing Bolton and others testify.

Sen. Lisa Murkowski, R-Alaska, talks to reporters as she leaves the Capitol in Washington, Jan. 28, 2020.

Bolton’s revelation in his soon-to-be-published book could blow up the White House’s major defense: that the president did nothing wrong in withholding $391 million in military aid to Ukraine.

Trump’s lawyers say he had the right to freeze the aid because he was concerned about Ukrainian corruption and wanted Europe to pitch in more to help Ukraine fight Russian-backed separatists.

Democrat impeachment managers say Trump abused his power and would not release the aid until Ukrainian President Volodymyr Zelenskiy publicly committed to investigating Trump’s rival for the 2020 White House, Democrat Joe Biden, for alleged corruption.

WATCH: Trump Team Closes Impeachment Defense


Defense rests

The Trump defense team wrapped up its case Tuesday. Lawyer Jay Sekulow told the 100 senators acting as jurors, “We are clear in our position there was no quid pro quo” in Trump asking Zelenskiy to investigate Biden.

Sekulow said Trump had “a proper government interest” to investigate possible corruption in asking for the Ukraine investigations of Biden, his son Hunter’s work at a Ukrainian natural gas company, and a debunked theory that Ukraine meddled in the 2016 U.S. presidential election that Trump won. No evidence has emerged of wrongdoing by the Bidens.

“He knew what he was saying,” Sekulow said of Trump’s July conversation with Zelenskiy. “To say he’s not acting in the national interest is wrong.” 

Personal attorney to President Donald Trump Jay Sekulow speaks during the impeachment trial against the president in the Senate at the U.S. Capitol, Jan. 28, 2020.

Sekulow’s arguments came on the third and last day of the president’s defense that he should be acquitted of two articles of impeachment — abusing the power of the presidency and obstructing congressional efforts to investigate his Ukraine actions.

“These articles must be rejected,” Sekulow said. “The Constitution requires it. Justice demands it.”

White House counsel Pat Cipollone concluded, “This should end now, as quickly as possible.”

“Nothing in the Bolton revelations, even if true, would rise to the level of an abuse of power or an impeachable offense,” famed attorney Alan Dershowitz said late Monday.

Debate Friday

A four-hour debate is expected Friday on whether to subpoena Bolton, whom Trump dismissed in September, and other witnesses familiar with Trump’s Ukraine-related actions and documents held by the White House and government agencies.

Trump’s Republican defenders have balked at calling Bolton as a witness.

“I think, at this point, if you want to hear from John Bolton, you have to ask yourself, ‘Is he a disinterested party? Is he a neutral party? Or is he someone who’s very unhappy — disgruntled, fired employee who now has a motive, a multimillion-dollar motive, to inflame the situation?” Senator Rand Paul asked.

Sen. Rand Paul, R-Ky., talks to reporters before attending the impeachment trial of President Donald Trump on charges of abuse of power and obstruction of Congress, Jan. 28, 2020, on Capitol Hill in Washington.

Trump’s lawyers sharply attacked Biden and his son’s lucrative work for a Ukrainian natural gas company. They accused Democrats of improperly using impeachment as a weapon to get rid of a president they simply don’t like, to overturn the 2016 election, and keep Trump off the ballot in November as he seeks a second term in the White House.

A two-thirds vote in the 100-member Senate is needed to convict Trump and remove him from office. But with Republicans holding a 53-47 majority and no Republican calling for his ouster, Trump is all but assured of being acquitted.