The Senate rejected an attempt on Tuesday to derail former President Trump’s impeachment trial by getting it declared unconstitutional. 

Senators voted 56-44 that the trial is constitutional. The vote required only a simple majority.

Six GOP senators joined with Democrats to say they believe the trial is constitutional, largely mirroring a similar vote from late last month. 

Only Sen. Bill Cassidy (R-La.), who had previously supported an effort by Sen. Rand Paul (R-Ky.) that would have declared the trial unconstitutional, flipped and said on Tuesday that he believes it is constitutional. 

Despite Cassidy's vote, the result again underscored the uphill battle Democrats face to get the 17 GOP senators needed to convict Trump.

Cassidy panned the presentation from Trump's team, contrasting it with the House impeachment managers he believes were more effective. 

"I said I'd be an impartial juror. Anyone listening to those arguments — the House managers were focused. They were organized. They relied upon both precedent, the Constitution and legal scholars. They made a compelling reason. President Trump's team was disorganized," Cassidy said. 

He added that "as an impartial juror, I'm going to vote for the side that did the good job."

GOP Sens. Susan Collins (Maine), Lisa Murkowski (Alaska), Mitt Romney (Utah), Ben Sasse (Neb.) and Pat Toomey (Pa.) had previously voted to say the trial was constitutional and voted the same way on Tuesday.

House impeachment managers and Trump's team spent hours debating if the trial was constitutional ahead of Tuesday's vote. That's a shift from last month's vote, where Republicans appeared caught off guard that Paul was forcing the issue.