WASHINGTON (CBSNewYork/AP) — Supreme Court Justice Anthony Kennedy said Wednesday he is retiring, giving President Donald Trump the chance to cement conservative control of the high court.

The 81-year-old Kennedy said he is stepping down, effective July 31, after more than 30 years on the court. 

A Republican appointee, he has held the key vote on such high-profile issues as abortion, affirmative action, gay rights, guns, campaign finance and voting rights.

“He’s been a great justice of the Supreme Court,” Trump said. “He’s displayed tremendous vision and tremendous heart.”

Kennedy sent his resignation letter to the president Wednesday afternoon.

“It has been the greatest honor and privilege to serve our nation in the federal judiciary for 43 years, 30 of those years on the Supreme Court,” Kennedy wrote, according to a release from the U.S. Supreme Court.

Without him, the court will be split between four liberal justices who were appointed by Democratic presidents and four conservatives who were named by Republicans.

Trump’s nominee is likely to give the conservatives a solid majority and will face a Senate process in which Republicans hold the slimmest majority however, Democrats can’t delay confirmation due to the adoption of the “nuclear option.” The new confirmation process requires only a simple majority to approve Supreme Court nominees.

The president said he’s considering a list of 25 candidates.

Trump’s first high court nominee, Justice Neil Gorsuch, was confirmed in April 2017.

The news of Kennedy’s retirement came the same day the Supreme Court issued a major blow to organized labor, CBS2’s Dick Brennan reported. In a 5 to 4 decision, the court ruled that government workers who choose not to join unions may not be required to help pay for collective bargaining.

Justice Samuel Alito wrote for the majority, saying, “It is hard to estimate how many billions of dollars have been taken from nonmembers and transferred to public-sector unions in violation of the First Amendment. Those unconstitutional exactions cannot be allowed to continue indefinitely.”

Illinois Gov. Bruce Rauner initiated the lawsuit in 2015.

“This is an historic victory for freedom of speech and also to defend taxpayers against conflicts of interest,” he said. “There are five million taxpayer-funded Americans who don’t want to necessarily be in a union, who now no longer are forced to fund union activity that they disagree with.”

Union members in New York City rallied against the ruling at City Hall.

Gov. Andrew Cuomo called the decision purely political and dismissed the high court’s argument that people have a right not to fund a union with a different political opinion.

“There’s already a provision where a member’s political dues can be returned if they disagree with the political opinion of the union. So that is nonsensical,” he said.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)