The Senate, he said, has no right to try a private citizen, which Trump now is. Thus, what we are about to do is flatly unconstitutional.

Forty-five of 50 Republican members agreed with Paul's motion.

"This vote indicates it's over. The trial is all over," said Paul.

"If you voted that (the Senate trial is) … unconstitutional, how in the world would you ever vote to convict somebody for this?"

Consistency says you would not.

Susan Collins of Maine, one of five Republicans who voted against Paul's motion, agreed that the vote portends the final vote on conviction.

"Do the math," Collins said. "It's extraordinarily unlikely the president will be convicted."

Rand Paul may have just derailed the second impeachment of Donald Trump.

Chief Justice John Roberts, the constitutional officer designated to preside over Senate impeachment trials, has said he will not preside over this latest trial of the ex-president. With Roberts seeing no constitutional duty, and declining the honor, his replacement as the presiding officer will be Patrick Leahy of Vermont, the longest-serving Democrat and the president pro tempore of the Senate.