Republicans outnumber Democrats, 51 to 49, in the Senate.
The vote is complicated by the absence of Sen.
Kennedy was long a swing vote on the nine-member court, and Trump's choice - his second opportunity in 18 months to fill a Supreme Court vacancy - will dramatically affect many aspects of American life, from abortion to voting rights to immigration.
Sen. Richard Blumenthal (D-Conn.) said Sunday President Trump is acting like a "puppet" for outside groups and claimed Trump is set to nominate a "fringe ideologue" to the Supreme Court. "So red-state Democrats are going to have a very hard decision".
Sen. Roy Blunt (R-Mo.) told NBC's "Meet the Press" that the Senate will be able to confirm Barrett, Hardiman, Kavanaugh, or Kethledge, but said picking a candidate who can be confirmed quickly is important.
"I'm not sure I'm leaning anywhere on those four nominees".
"I will oppose the nomination the President will make tonight because it represents a corrupt bargain with the far Right, big corporations, and Washington special interests", Casey said in a statement. "I don't think my role is to rubber stamp for the president, but it's also not an automatic knee-jerk no, either". Trump had a strong favorable reaction to Kethledge, while Barrett was seen as a less likely choice.
The White House said Trump has interviewed four potential picks, all of whom are federal appeals court judges. The group already has created a web video warning of Trump's pick, and is already running spots in ME and Alaska focusing on Roe v. Wade. Sen. But in terms of selecting his nominee, the president said he would not use Roe v. Wade as a litmus test for a nominee.
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In a recent interview, he signaled that he may be willing to cooperate with special counsel Robert Mueller's investigation. He indicated it is increasingly unlikely, though not impossible, Trump will volunteer to be interviewed.
"Beyond the procedure, beyond the gamesmanship, it is a life-and-death important decision to be made by this court on so many issues", Senator Dick Durbin of IL, the body's No. 2 Democrat, said Sunday on NBC.
Every Republican voted past year to confirm Associate Justice Neil M. Gorsuch, who filled the vacancy left on the court by the late Antonin Scalia.
Any one of them could tip the balance of the nine-person court toward conservatives and revisit landmark rulings on abortion access, racial discrimination, gay rights and other issues. Previously, Collins voted for Gorsuch because of his belief in the significance of precedent.
During Trump's presidential campaign, he emphasized that he would appoint conservative justices to the Supreme Court bench if he was elected. Many, including Leo, believe that it was a major contributing factor to his victory in 2016.
Kavanaugh, 53, was picked by former President George W. Bush to serve on the influential Washington-based appeals court in 2003. As an appeals court judge, Kethledge authored several notable opinions, including one that upheld the death penalty against a suspect who murdered a woman on federal land and a case in OH that questioned whether private citizens can sue the state for failing to enforce pollution controls.
The Democrats' dilemma is all the more profound because of the party's own decisions in the Barack Obama years, when, as the majority in the Senate, they began to change the arcane rules governing the chamber's proceedings.
Barrett, who is 46, has less of a judicial record to review, having just been nominated to the appeals court by Trump a year ago.
Of the other two, he added: "Ray Kethledge and Tom Hardiman, they're a little bit less known by conservatives".