Republican Senator Susan Collins said she believes President Trump has learned a "pretty big lesson" by being impeached and plans to vote to acquit him. In an interview with "CBS Evening News" anchor Norah O'Donnell on Tuesday, Collins acknowledged there may be voters in her home state of Maine who will be "unhappy" with her decision.

"All I can do is apply the constitutional standard. And that's my job. My job is not to weigh the political consequences, but to do impartial justice to live up to the oath that I took," Collins said.

The Senate plans to vote Wednesday on whether to convict the president on two articles of impeachment: abuse of power and obstruction of Congress. Collins was one of only two Republicans who voted to allow witnesses in the impeachment trial. But even without witnesses, Collins said she doesn't believe Mr. Trump's behavior "reaches the high bar in the Constitution for overturning an election."

Senator Susan Collins speaks to "CBS Evening News" anchor Norah O'Donnell on Tuesday, February 4, 2020. CBS News

Read more of O'Donnell's interview with Collins below.

Norah O'Donnell: Senator Collins, thank you so much for joining us. Was the president's call a perfect call?

Senator Susan Collins: No. It was not. The president's call was wrong. He should not have mentioned Joe Biden in it, despite his overall concern about corruption in Ukraine.



O'Donnell: Why was it wrong for the president to mention the Bidens in that July phone call?



Collins: Because the president of the United States should not be asking a foreign country to investigate a political rival. That is just improper. It was far from a perfect call.



O'Donnell: You call the president's actions wrong, improper — that they showed very poor judgment, in your words. Should the president apologize or acknowledge what he did was wrong?

Collins: I think that would be helpful. President Clinton did that in 1999. It took him a while. But finally, he did apologize for his actions.



O'Donnell: Will you support Senator Joe Manchin's censure resolution?



Collins: I think we're past that point. We've had the president impeached. That is a far greater sanction than a censure. I think we're past that stage.



O'Donnell: Article 1 alleges the president, "Will remain a threat to national security and the constitution if allowed to remain in office." Are you confident that the president won't seek foreign assistance again?



Collins: I believe that the president has learned from this case.



O'Donnell: What do you believe the president has learned?



Collins: The president has been impeached. That's a pretty big lesson. I'm voting to acquit. Because I do not believe that the behavior alleged reaches the high bar in the constitution for overturning an election, and removing a duly elected president.



O'Donnell: But the president says he did nothing wrong. Why do you think he learned something?



Collins: He was impeached. And there has been criticism by both Republican and Democratic senators of his call. I believe that he will be much more cautious in the future.



O'Donnell: So, do you believe the president's actions were criminal?



Collins: I do not. In the actual articles of impeachment, there are no accusations that the president broke the law.



O'Donnell: And yet, according to U.S. law, it is unlawful to solicit help from a foreign national directly or indirectly. That's illegal.



Collins: But again, the House managers did not make that case in the articles of impeachment. And I actually raised the issue with the House managers, and they failed to give me a response to that question. I suspect it's because they could not prove all of the elements of the crime.



O'Donnell: The House issued 23 subpoenas for current and former administration officials. The White House did not comply. Is that obstruction?



Collins: There's nothing wrong with a party exercising their constitutional rights. The House issued those 23 initial subpoenas before the impeachment inquiry was even authorized. And then the House never even issued a subpoena to John Bolton, whom the House has repeatedly called as the key witness in this impeachment proceeding--



O'Donnell: And yet, you were the one who pushed the Republican leader Mitch McConnell to include that provision to vote for witnesses. Do you believe the record is incomplete?



Collins: I believe that the record is sufficient. There were 17 witnesses, 2,700 documents for me to reach a decision.



O'Donnell: You made an interesting observation in terms of Article II, obstruction of Congress, that the House managers made the case that impeachment was a last resort.



Collins: I believe they used it as a first resort, and that they sacrificed speed for finality. They never bothered to subpoena John Bolton at all, despite naming him as a key witness.



O'Donnell: Do you think that was the fatal flaw?



Collins: I think it's certainly was an important flaw, and caused them to present a case that was weaker than it should have been. Instead, they were bound by an artificial deadline. And yet, they waited 33 days to submit the articles of impeachment to the Senate.



O'Donnell: Was this a difficult decision for you?



Collins: It's always difficult when you're looking at the facts of a case, and you don't approve of the conduct of the individual. The framers did not intend for impeachment to be used as a political weapon, or to be used frequently. It was to be rare. So when I applied the standard in the Constitution, it became evident to me that despite the president's poor judgment, he did not reach the standard for removal.



O'Donnell: Tonight the president will give his State of the Union address, just hours before the final vote on impeachment. Does the president need to address impeachment in his State of the Union?



Collins: He does not. And he should not.



O'Donnell: Why?



Collins: The president should focus on his vision for our country, the policies that he wants to get through in the next year.



O'Donnell: You're up for re-election this year. Do you believe you will pay a political price for this vote?



Collins: I'm sure there are going to be people unhappy with me in Maine. All I can do is apply the constitutional standard. And that's my job. My job is not to weigh the political consequences, but to do impartial justice to live up to the oath that I took.



O'Donnell: Senator Susan Collins. Thank you.

Collins: Thank you.