WASHINGTON (NEXSTAR) — U.S. senators started asking their questions on Wednesday in the impeachment trial of President Donald Trump.

Senators wrote down their questions and the chief justice asked them, then the legal teams got five minutes to answer.

The biggest question may still be whether the Senate will call witnesses.

“All-hands-on-deck effort to say shut this thing down before we expose the amount of corruption that existed within the administration,” said Sen. Jeff Merkley (D-OR).

Merkley said the White House is pressuring Republicans to vote against calling witnesses.

“Arms are being twisted as we speak and pressure is being applied,” he said.

At least three Republican senators appear to be resisting the pressure so far. But Sen. Cory Gardner (R-CO), who might have been the deciding vote for witnesses, has said he’s seen enough.

So has Republican Sen. Marsha Blackburn of Tennessee.

“You know what? We don’t need more witnesses. The House called 17 witnesses,” Blackburn said.

But Washington Sen. Patty Murray said witnesses are critical to a fair trial.

“Making it all the more urgent that we hear not just from John Bolton, but from other key advisers to the president who were involved with his actions in Ukraine,” Murray said.

The White House has issued a letter in an effort to block the release of parts of Bolton’s book, saying it contains top-secret, classified information.

Sen. Martin Heinrich (D-NM) wants to know what the president’s legal team knew about Bolton’s book.

“The White House was sitting on a manuscript that they were reviewing that had a first-person account who was in the room saying, effectively, yes there was a quid pro quo,” Heinrich said.