President Trump said Thursday his administration has already begun the process of considering possible replacements for retiring Supreme Court Justice Anthony Kennedy, calling it “the most important decision a president can make.”

“We've already started,” Trump said during a speech in Wisconsin. “And, hopefully, we're going to make you very proud.”

Kennedy announced his retirement from the high court on Wednesday afternoon. Trump has said he will choose a replacement from his previously released list of 25 candidates.

“We're going to pick ourselves one great United States Supreme Court justice to take the place of a great man, Justice Kennedy, really a great person, great man,” Trump said Thursday.

Trump boasted that his first Supreme Court pick, Justice Neil Gorsuch, has made conservatives happy.

KENNEDY RETIREMENT KICKS SPECULATION OVER SUPREME COURT REPLACEMENT INTO HIGH GEAR

“We had a fantastic choice with Justice Gorsuch, very proud of it, doing a fantastic job,” he said. “And we're going to try and do just as good.”

Sources indicated to Fox News six federal appeals court judges -- Thomas Hardiman, Brett Kavanaugh, Amy Coney Barrett, Amul Thapar, Joan Larsen and Raymond Kethledge -- are considered early frontrunners. All six of these judges are on Trump's list.

During a rally in North Dakota on Wednesday, Trump praised the retiring Kennedy as "a very special guy" and "a great man," telling the crowd he was "very honored" Kennedy chose to retire while Trump was in office because "he felt confident in me to make the right choice and carry on his great legacy."

"Justice Kennedy's retirement makes the issue of Senate control one of the vital issues of our time," Trump said. "It's the most important thing we can do ... We must elect more Republicans. We have to do that. And the problem is, in the Senate, we have 51. We don't have enough."

Fox News’ Samuel Chamberlain contributed to this report.