If Democrats open “a can of worms” by calling witnesses during former President Donald Trump’s impeachment trial, Senate Republicans will call on the FBI to testify, Sen. Lindsey Graham (R-S.C.) said, Fox News reported.

The trial is set for next Tuesday.

Democrats are expected to announce as soon as Tuesday whether they will call witnesses, Reuters reported Monday.

“If you open that can of worms, we’ll want the FBI to come in and tell us about how people pre-planned this attack and what happened with the security footprint at the Capitol,” Graham told Fox News host Sean Hannity on Monday night. “You open up Pandora’s Box if you call one witness.”

In the same interview, Graham said that the “second impeachment of Donald Trump is not wearing well over time. Democrats are in a box.”

Senate Minority Leader Mitch McConnell (R-Ky.) has not publicly stated his views on impeachment yet, but he did say on the Senate floor last month that the mob who violently stormed the U.S. Capitol on January 6 were “provoked” by Trump and “other powerful people.” Last week, too, McConnell voted with 44 other Senate Republicans against tabling a vote on the constitutionality of Trump’s second impeachment, the first time a commander-in-chief has received an impeachment trial in the upper chamber after leaving office. The vote was ultimately tabled.

Graham provided his insight into what Senate Republicans think of impeachment.

“I had a great meeting with Sen. McConnell today, I think every Republican sees the House process as an affront to the presidency and due process,” the South Carolina Republican said.

Exactly one week after the deadly January 6 riot, the House of Representatives voted 232-197 to impeach Trump for “incitement of insurrection.”

When asked about the concerns surrounding the constitutionality of impeaching a former president, Graham said, “Sen. McConnell basically told the Republican conference exactly what you just said. He was offended by the process in the House.”

The trial scheduled to start February 9 will be overseen by Senate President Pro Tempore Patrick Leahy (D-Vt.) instead of Supreme Court Chief Justice John Roberts.

Trump allies have put it out in the open that the main argument they plan to make is that the impeachment trial is unconstitutional since the former president has already left office.

In order to successfully convict Trump, 17 Republicans would have to break party lines and vote will with all 50 members of the Senate Democratic Caucus. However, 45 Republican senators including McConnell voting last week to not table a vote on the trial’s constitutionality has been widely interpreted to mean that the trial will be dead on arrival next week.

You can follow Douglas Braff on Twitter @Douglas_P_Braff.