A Long Island man was busted for making death threats against GOP U.S. Senators Chuck Grassley and Susan Collins for their support of then-Supreme Court nominee Brett Kavanaugh, The Post has learned.

Ronald DeRisi, 74, was taken into custody early Friday, and is expected to be arraigned later in the day in Central Islip federal court before Magistrate judge Gary R. Brown.

The Smithtown man is accused of leaving disturbing voicemails on the senators’ office phones following their public support of Kavanaugh’s nomination and confirmation, in an attempt to discourage the pols from voting in the jurist’s favor, a source familiar with the case revealed.

In one message left on September 27, DeRisi allegedly said that he had a “present” for Iowa’s Grassley, growling, “It’s a 9 millimeter. Side of your f—ing skull you scumbag motherf—–r.”

The message concluded: “Yeah, Kavanaugh – I don’t think so.”

In another rant aimed at the 85-year-old senator, DeRisi was recorded saying “We’re tired of this guy sucking taxpayers’ money! Getting a free f—ing ride! How many more years you gonna do it? None! He’s a dead man! 9 millimeter, side of the f—-ing head! If f—ing Kavanaugh gets in, he’s dead f—ing meat! Actually even if Kavanaugh doesn’t get in he’s dead f—ing meat. 9 millimeter, side of the head, you f—ing old bastard.”

Most of the calls were placed from a pre-paid cell phone, according to court docs.

DeRisi took a different tone with Collins, of Maine, calling her a “twit” on the day of the vote.

“I’m gonna get you,” he’s accused of saying. “You better pray this guy don’t get in.”

He left another message two minutes later, saying: “tick-tock, tick-tock, tick-tock.”

Less than an hour later, Collins received another message from DeRisi.

“Listen, you dumb son of a bitch, don’t you know that guy’s a sex offender? How could you not know that…you f–king twit.”

DeRisi pleaded guilty in Nassau County in 2015 to one count off aggravated harassment, for repeatedly calling his target’s office more than 15 times, and leaving threatening voicemails. It’s not clear if that victim was also a public figure.

A message to DeRisi’s residence was not immediately returned.

Reps for Collins did not return requests for comment, while Grassley’s office referred the Post to the Public Information Office of the United States Capitol Police, who also declined to comment.

“Representative democracy cannot work if elected officials are threatened with death for simply doing their job,” United States Attorney Richard Donoghue said in a statement. “The First Amendment – the pinnacle of American achievement – protects debate, disagreement and dissent, not death threats. We and all those dedicated to the rule of law will not tolerate the use violence and threats of violence in attempts to prevail in political disputes.”