As of Sunday, Trump said he had yet to make a decision on who to nominate.
While the president has been pondering his pick, aides have been preparing for a tough confirmation fight.
Savoring the suspense, Trump has sought to keep people guessing in the final hours, hoping to replicate his successful announcement of Justice Neil Gorsuch a year ago.
Kennedy said he was bracing for a tough confirmation battle as Democrats focus on the nominee's views of the high court's Roe v. Wade ruling legalizing abortion.
Relishing the suspense, Trump insisted he still hadn't locked down his decision, which he wants to keep under wraps until a 9 p.m. Monday announcement from the White House. But the situation appeared to remain fluid. Let's say it's the four people. Hardiman, who lives in Pennsylvania, is a judge on the U.S. Court of Appeals for the 3rd Circuit, where he served at one time with Trump's sister, Judge Maryanne Trump Barry.
During Trump's presidential campaign, he emphasized that he would appoint conservative justices to the Supreme Court bench if he was elected.
Kavanaugh, 53, earned his law degree from Yale University and was also an editor on the prestigious Yale Law Journal. But his supporters cite his experience and wide range of legal opinions.
Kethledge, 51, is a University of Michigan Law School graduate and former Kennedy law clerk who works out of an office he set up in an old barn overlooking Lake Huron in northern Michigan.
Barrett - a longtime Notre Dame Law School professor who became a federal judge last fall - excited social conservatives since she was questioned about her Roman Catholic faith in her nomination hearings previous year, but her brief time on the bench has raised questions about her experience. Previous lobbying efforts by McConnell - including a push for fellow Kentuckian 6th Circuit Court of Appeals Judge Amul Thapar, who would have been the court's first Asian-American nominee - have failed. A self-described introvert, Kethledge co-authored a book, "Lead Yourself First", in which he talks about how some of the world's great leaders learned from solitude and quiet.
"In a nation with over 700 sitting federal judges, many of whom were appointed by Republican presidents, it is outrageous that President Trump will nominate from a list of just 25 dictated to him by the Heritage Foundation", Casey said in a statement Monday. On Saturday, he tweeted that a "Big decision" was coming soon.
The president and White House officials involved in the process have fielded calls and messages and have been on the receiving end of public pleas and op-eds for or against specific candidates since Kennedy announced on June 27 that he would retire this summer.
Sen. Lindsey Graham (R-S.C.) spoke out about this concern on the air with Fox News on Sunday. Both are conservative jurists in the mold of Trump's previous Supreme Court pick, Gorsuch. Dick Durbin of IL on NBC's "Meet the Press" said Sunday. "I'm very confident with this president's enthusiasm and with Leader McConnell's enthusiasm that they can get anybody confirmed".
Leo, who had helped Trump compile the original list of nominees, said that he would pick Kavanaugh, with Kethledge and Barrett a close second.