WASHINGTON (Reuters) - A judicial activist advising U.S. President Donald Trump on potential nominees to the Supreme Court signaled on Sunday that two of the candidates would be a tougher sell to conservatives.

Leonard Leo said two names on the president’s short list to succeed retiring Justice Anthony Kennedy - Raymond Kethledge and Thomas Hardiman - had less-established conservative records, making it harder to line up support should they be selected.

“I think in regards to Kethledge and Tom Hardiman they are a little less known by conservatives and their records are a little bit lighter so it might take some time,” Leo told ABC’s “This Week” on Sunday. “It’s important to have people who are extremely well known and have distinguished records.”

Leo said, however, that Trump would ultimately succeed at lining up conservative support for anyone he selected.

Democrats see the seat being vacated by Kennedy, a conservative judge who sometimes sided with the court’s liberal wing, as critical to maintaining abortion rights and key provisions of former Democratic President Barack Obama’s healthcare plan.

Reuters reported last week that conservative federal appeals court judges Kethledge and Brett Kavanaugh were the two most serious contenders being considered by Trump for the Supreme Court, citing a source familiar with the process.

Trump said on Sunday he expected to decide on the nominee sometime on Sunday night or Monday. “I’m getting close to making a final decision and I believe the person will do a great job,” he told reporters before boarding Air Force One to travel back to Washington from his New Jersey golf club.

Kavanaugh, 53, was picked by former Republican President George W. Bush to serve on the influential Washington-based appeals court in 2003. Kethledge, 51, is a judge for the Cincinnati-based 6th U.S. Circuit Court of Appeals, while Hardiman, 52, serves on the Philadelphia-based 3rd U.S. Circuit Court of Appeals. Hardiman and Kethledge were also appointed by Bush.

The source told Reuters that Amy Coney Barrett of Indiana, a Trump-appointed judge on the Chicago-based 7th U.S. Circuit Court of Appeals, was still in contention but that the Republican president had been asking more questions about the other two, who have more extensive judicial records.

Democratic lawmakers, who have a minority of seats in both houses of Congress, have acknowledged there is no clear path to block Trump’s pick for the lifetime appointment to the Supreme Court.

While the U.S. Senate once required a 60-vote supermajority to overcome blocking tactics against Supreme Court nominees, the Republican majority changed the rules last year during the debate on Justice Neil Gorsuch.

Senate rules now require only a simple majority of votes to confirm a Supreme Court nomination. Republicans currently control 51 of the 100 Senate seats, although one of their number, Senator John McCain, is at home in Arizona battling cancer.

“If all the Republicans stick together,” Chris Coons, a Democratic senator on the Senate Judiciary Committee, told CBS’ “Face the Nation” on Sunday, “they will be able to confirm whomever President Trump nominates.”