Senate Judiciary Committee Chairman Chuck Grassley, R-Iowa, told Fox News on Tuesday night that he wanted to help raise $3 million in support of Sen. Susan Collins, R-Maine, amid a barrage of criticism over her vote to confirm Brett Kavanaugh to the Supreme Court and a fundraising campaign seeking to oust her in 2020.

Collins was a key swing vote in the battle to confirm Kavanaugh and her 45-minute speech on the Senate floor announcing her "aye" vote last week virtually ensured his ascension to the high court. Since then, former National Security Adviser Susan Rice has floated running against Collins and a crowdfunding campaign started by Maine progressive groups to fund the Republican's future opponent has raised more than $3.3 million. The groups -- Be A Hero Team, Maine People's Alliance and Mainers for Accountable Leadership -- said Collins' re-election campaign would have received the money if she'd voted against Kavanaugh's confirmation.

Grassley called the criticism of Collins "abominable" in an interview with Fox News' "The Story with Martha MacCallum."

"It just goes to show you how narrow the thinking of the opposition to Kavanaugh was, that they would say those extremist ... positions about a person that's been with them most of the time," Grassley said.

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For her part, Collins accused the groups behind the fundraising campaign of trying to buy votes in an interview with CBS' "60 Minutes" on Sunday.

"This is a classic quid-pro-quo as defined in our bribery laws," Collins said, adding: "I think that if our politics has come to the point where people are trying to buy votes and buy positions, then we are in a very sad place."

Grassley also told Martha MacCallum that if he still chaired the Senate Judiciary Committee, it would not consider a Supreme Court nomination if a vacancy came up in 2020.

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"I pledged that in 2016," said Grassley, referring to Senate Majority Leader Mitch McConnell's decision not to give Obama nominee Merrick Garland a hearing after the death of Antonin Scalia.

"If somebody else is chairman of the committee, they'll have to decide for themselves," Grassley said. "But that's the decision I made a long time ago."

Fox News' Martha MacCallum and Mike Arroyo contributed to this report.