By Ariane de Vogue and Joan Biskupic

CNN

(CNN) -- Justice Neil Gorsuch has been on the bench for less than a month and conservatives are already preparing for the next Supreme Court confirmation fight. The only hitch: there's no vacancy.

But that hasn't stopped some Republicans, including President Donald Trump, from talking openly about a next seat and even possibly trying to woo 80-year-old Justice Anthony Kennedy into retirement.

Friends and associates believe Kennedy is seriously considering retirement. In general, the burdens of age and demands at the court weigh in one direction. His deep interest -- and leading role -- in America's constitutional democracy weigh in the other.

The question appears not to be whether Kennedy will retire soon, but when -- at the end of this June, or next?

Replacing staunch conservative Justice Antonin Scalia with the likeminded 49-year-old Gorsuch may not change the direction of the court. The political and legal stakes, however, would be dramatically higher if Trump has the opportunity to fill Kennedy's seat. Kennedy, a centrist conservative, has cast a key vote for gay marriage, abortion rights, affirmative action, and fair housing law.

Kennedy controls the outcome of cases like no other justice in more than a decade. With four conservatives to his right, four liberals to his left, he often holds the decisive vote on business and regulatory matters as well.

In response to a request from CNN, Kennedy, a 1988 appointee of Republican President Ronald Reagan, declined to comment on his retirement plans. He also declined to respond to questions related to any private meeting with anyone from the Trump administration.

Trump told the Washington Times this weekend he wasn't aware of any specific plans for Kennedy to retire.

"I don't know. I have a lot of respect for Justice Kennedy, but I just don't know," Trump said. "I don't like talking about it. I've heard the same rumors that a lot of people have heard. And I have a lot of respect for that gentleman, a lot."

Who's on the list?

Conservatives and liberals are already preparing game plans, irrespective of when a new vacancy arises.

And because the Gorsuch filibuster prompted Senate Republicans to change the rules and make it easier to confirm Supreme Court justices, Democrats will have a harder time blocking any Trump nominee. It now takes only 51 senators -- a simple majority -- to clear nomination.

Sources close to the process say there have been discussions about potential replacements for Kennedy if the seat were to open up. Some of the names discussed include former clerks and others from Trump's original list of 21 possible nominees he released during the campaign who might appeal to Kennedy.

That would include those who were on Trump's previous lists: Judge Raymond M. Kethledge of the US Court of Appeals for the 6th Circuit, who is a former Kennedy clerk, and Judge Thomas Hardiman of the 3rd Circuit, who was a runner up for the Scalia seat.

Also in the mix could be Sen. Mike Lee of Utah, and Judge Amul Thapar, United States District Court for the Eastern District of Kentucky, currently up for an appellate court seat on the 6th Circuit with the support of Senate Majority Leader Mitch McConnell of Kentucky.

Asked by the Washington Times if he will use the campaign list again, Trump said, "Yes. That list was a big thing."

But also in play this time around could be a former Kennedy clerk, Judge Brett Kavanaugh of the United States Court of Appeals for the District of Columbia, as well as former Solicitor General Paul Clement. They were left off the last list in part because the President wanted to choose from individuals outside the District of Columbia. That move, one source said, was in harmony with his "drain the swamp" campaign promise.

Over the past three decades, justices have often chosen spring to announce their retirements, as the annual October-June session was winding down.

Eight years ago on May 1, Supreme Court Justice David Souter sent a letter to President Barack Obama declaring he would retire when the session ended in June. The White House, expecting word for months, was ready with a list of possible successors and had already contacted some, including Sonia Sotomayor, who eventually got the appointment in 2009.

Some key senators appear ready.

Two weeks ago, Senate Judiciary Committee Chairman Chuck Grassley said he expected another resignation this summer.

"I have no way of knowing who it is, it's just a very general rumor for the last six months around Washington, DC and I assume it's somebody in their late seventies or early eighties," Grassley told reporters. That would apply to Justice Ruth Bader Ginsburg (84), Stephen Breyer (78) and Kennedy. It is unlikely that Ginsburg or Breyer, appointees of Democratic President Bill Clinton, would choose to retire under a GOP president.

"I think we'll have another Supreme Court vacancy this summer," Texas GOP Sen Ted Cruz told a gathering at the Conservative Political Action Conference earlier this year. He suggested that if Kennedy or one of the liberal justices step down, the left "will go full Armageddon meltdown."

And the President -- who said during the campaign that he expected several vacancies -- himself heightened the interest in Kennedy with a brief exchange just before the President's first address to Congress in February.

As he made his way to the front of the House chamber, he shook hands with Justices Elena Kagan, Stephen Breyer, Sonia Sotomayor and Chief Justice John Roberts. But Trump stopped to talk to Kennedy about their children who live in New York.

"Thank you, that's very nice coming from you. Say hello to your boy. He's a special guy," Trump said.

"Your kids have been very nice to him," Kennedy responded.

"Well they love him in New York," Trump said.

And in late February, Ivanka Trump and her daughter attended oral arguments at the Supreme Court as guests of Kennedy. A court spokeswoman said that Ivanka had met the justice at the inaugural lunch after her father's swearing-in ceremony at the Capitol.

Ivanka and her daughter sat in the most exclusive section of the white marble, red velvet courtroom, in seats usually reserved for the justices' family and special guests.