This summer, President Trump will get his second Supreme Court pick.

Supreme Court Justice Anthony Kennedy on Wednesday announced that he will retire, effective July 31, after serving three decades on the highest court.

“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 said in a statement. According to the court’s press release, the justice “added that while his family was willing for him to continue to serve, his decision to step aside was based on his deep desire to spend more time with them.”

After a successful nomination by President Ronald Reagan, Kennedy took office February 18, 1988, and has since become a pivotal moderate, swing-voting member of the court.

The vacancy will create a heated fight in the Senate over his successor, who will have the opportunity to change the court for decades. Trump has already appointed conservative Justice Neil Gorsuch, who replaced the late Antonin Scalia last year after Republicans stalled the confirmation of former President Barack Obama’s pick Merrick Garland.

Following the news, Trump said he will “immediately” begin a search for his new nominee, per the Associated Press, and called Kennedy a man of “tremendous vision.”

With Kennedy gone, Chief Justice John Roberts (who is more definitively conservative than Kennedy ever was) now becomes the most central justice and likely swing voter.

Though he was appointed by Reagan, Kennedy has played a key role in some landmark liberal court decisions, much to the chagrin of conservatives.

The Washington Post reported that his vote to uphold the “basic underpinnings” of Roe v. Wade—which effectively legalized abortion—has long upset the right.

Beyond that, Kennedy wrote each of the court’s major decisions on gay marriage, most famously Obergefell v. Hodges, which affirmed the constitutionality of same-sex marriage across the United States. Kennedy’s vote also famously upheld the Affordable Care Act in the 2012 King v. Burwell case.