Collins, who voted for Kavanaugh in what she termed one of her hardest decisions ever, said in response to a question about a potential challenge from former U.S. National Security Adviser Susan Rice that she did what she thought was right.
Following Kavanaugh's confirmation, Republican leaders invoked the word in an attempt to paint Democrats as "angry" and desperate to block the conservative majority. He emphatically denied the allegations.
Bush called a number of senators in recent weeks, and had several conversations with Collins to reassure the key Republican vote about Kavanaugh's character and temperament, a person familiar with the matter said.
To cheers of supporters at the Kansas Expocentre in Topeka, Trump declared it a "historic night", not long after signing the paperwork to make Kavanaugh's status official.
Kavanaugh was confirmed to the court on Saturday by a razor-thin margin in the Senate, ending months of partisan rancor over his nomination and offering Donald Trump one of the biggest victories of his presidency. "I stand before you today on the heels of a tremendous victory for our nation", he said to roars.
A separate, public swearing-in ceremony is planned for 7:00 pm (2300 GMT) Monday in the White House's East Room.
Before her speech, protesters could be overheard chanting, "Vote no!"
The dispute over Kavanaugh has added fuel to campaigning for the elections in November when Democrats will try to take control of Congress from the Republicans.
Protesters rallied in Washington and other USA cities against the ascent of the 53-year-old judge, who has faced multiple allegations of sexual misconduct and been criticised for his angry partisan rhetoric.
GOP operatives say they are seeing renewed Republican interest in states such as Wisconsin, where Democratic candidates have been polling strong.
Heitkamp added, "I think that the politically expedient vote here was a "yes" vote".
Senator Collins arrives for the crucial vote.
Manchin used an emailed statement to announce his support for Kavanaugh moments after Collins finished talking.
"We simply followed the tradition in America, which is that if you have a Senate of a different party than the President you don't fill a vacancy created in a presidential (election) year", said McConnell on Fox News Sunday.
Mr Trump's choice of Judge Kavanaugh to replace Anthony Kennedy on the Supreme Court was controversial from the beginning, but initial concerns were based around his conservative views.
The brutal hearing sparked a supplemental Federal Bureau of Investigation dive into Kavanaugh's background and a week-long delay of the Senate vote. During a campaign rally in MS, the president mocked Ford for not remembering key details of the alleged attack, including the date and location of the party she says she and Kavanaugh attended 36 years ago.
Lisa Banks, another of Ford's attorneys, told MSNBC that Ford had no regrets about coming forward because she "still believes it was the right thing to do".
"When you blocked Merrick Garland's nomination from President Obama, you basically said that we don't do this in a presidential election year and that we wait until the election and then whoever the people choose, they get to pick the Supreme Court nominee. All of us have been hearing stories and accounts from survivors going back many, many years where they kept all these painful, traumatic accounts to themselves".
A few Republican senators who had wavered over whether to vote for Kavanaugh finally backed him this week, saying they did so in part because a brief FBI investigation found no corroborating evidence of Ford's accusations.
His nomination has been met with loud protests, both in Washington and in other cities across the United States. But they were not immediately visible in the area around the legislature. Ms Murkowski opposed it but asked to be recorded as "present".