U.S. Sen. Susan Collins on Wednesday blasted individuals who left vulgar and insulting messages with her office staff while urging her to vote against controversial Supreme Court nominee Brett Kavanaugh.

Progressive groups have been ramping up the pressure on Collins to vote “no,” arguing that Kavanaugh will likely be the deciding vote to overturn the 1973 Roe v. Wade Supreme Court case guaranteeing a woman’s right to abortion, or on other cases that would restrict women’s right to choose.

Collins, a moderate Maine Republican, said she remains undecided on Kavanaugh, but she sharply criticized escalating rhetoric about the upcoming vote on President Trump’s nominee, as well as a fundraising campaign that will funnel money to a potential Democratic opponent in 2020 if she votes to seat Kavanaugh.

Collins has likened the crowdfunding effort, which will only charge donors if Collins votes to approve Kavanaugh, to bribery. The campaign has raised nearly $1.2 million as of Wednesday afternoon, mostly with donations of $20.20.

Collins and U.S. Sen. Lisa Murkowski of Alaska are pro-choice Republicans – the GOP holds a 51-49 majority in the Senate. The two have been targeted by progressive groups trying to persuade them to oppose Kavanaugh.

The Senate votes to confirm or reject Supreme Court nominees.

One of the obscene messages, a letter to Collins’ Portland office that was first released to NBC News and subsequently sent to other media outlets, said that “EVERY waitress who serves you is going to spit in your food, and that’s if you’re lucky, you (expletive), (expletive)! Think of that every meal.”

Collins, in an interview with The Wall Street Journal, said the messages are “incredibly offensive.”

“In one case — and we are going to turn this over to the police, but unfortunately, of course, the person didn’t leave a name or number — but they actually threatened to rape one of my young female staffers,” Collins told the Journal.

A number of Collins’ Republican colleagues in the Senate stepped up to her defense Wednesday, including U.S. Sens. Ted Cruz of Texas and Orrin Hatch of Utah.

“The harassment campaign from the far Left against Susan Collins — including threats of sexual violence against her staffers and potential illegal bribery — is truly shameful, and shows the desperation of the radicals to try to stop the confirmation of Judge Kavanaugh. It won’t work,” Cruz wrote in a tweet.

Hatch tweeted, “Every Democrat should be condemning these antics in Maine — attempting to bribe Senator Collins to vote against Judge Kavanaugh and threatening sexual violence against staffers if she votes for him is absolutely disgusting.”

Marie Follayttar Smith of Mainers for Accountable Leadership, which organized the crowdfunding campaign with the Maine People’s Alliance and national health activist Ady Barkan, said they encourage people to be respectful when contacting Collins’ office.

But, she said, people’s passions are running high because Roe v. Wade hangs in the balance with the Kavanaugh vote. The Supreme Court is split 4-4 among conservative and liberal justices.

President Trump has previously said he would nominate a judge who would overturn Roe v. Wade. However, Collins has said she has been encouraged by Kavanaugh’s characterization of Roe as “settled law” and “precedent upon precedent.”

“People are engaged over this nomination more than ever,” Follayttar Smith said. “These are very high stakes.”

Barkan disputed Collins’ characterization of the crowdfunding campaign as “bribery,” noting that the individual donations are small and numerous — more than 42,000 as of Thursday — and would go to an as-yet unnamed opponent.

Barkan said in a statement that Collins was “smearing a grass-roots effort from regular people (who are) pleading with someone in a position of power to do the right thing.”

Collins, however, called it “a quid pro quo fundraising” that was “the equivalent of an attempt to bribe me to vote against Judge Kavanaugh.”

U.S. Sen. Susan Collins, R-Maine, makes her way through a crush of reporters on Capitol Hill in Washington on Dec. 1, 2017. (AP file photo)