WASHINGTON — Senator Susan Collins, Republican of Maine, said on Tuesday that she would vote to acquit President Trump of abuse of power and obstruction of Congress, calling his conduct “wrong” but saying she could not support removing him from office.

“I do not believe that the House has met its burden of showing that the president’s conduct, however flawed, warrants the extreme step of immediate removal from office,” Ms. Collins said in a speech from the Senate floor.

Ms. Collins, a moderate who is facing a steep re-election challenge this year, was one of only two Republicans to break with the party last week and vote in favor of considering new witnesses in Mr. Trump’s impeachment trial. But in announcing her vote on the verdict on Tuesday, she joined a growing chorus in her party who has argued that removing the president for his misconduct little more than nine months before he faces re-election was excessive.

“It is my judgment that except when extraordinary circumstances require a different result, we should entrust to the people the most fundamental decision of a democracy — namely who should lead their country,” Ms. Collins said.