President-elect Donald Trump has not been sworn in, nor has he said whom he intends to nominate to the Supreme Court once he is inaugurated. But a key activist group is starting to mobilize for the bare-knuckle fight that is sure to follow that nomination.

The Judicial Crisis Network is launching more than a half-million dollars in TV and digital ads Sunday that feature Trump’s remarks on the Supreme Court from the final presidential debate — “It’s just so imperative that we have the right justices” — along with a message asking viewers to thank Trump for pledging to nominate conservative jurists to replace the late Justice Antonin Scalia.

“The American people want justices that are strong and independent to protect our Constitution and make sure its meaning is preserved,” a narrator says. “And because of Donald Trump, the next Supreme Court justice will do just that.”

The ad, set to air in the Washington, New York and South Florida media markets, serves several purposes. One, it reminds conservative voters of a big reason they supported Trump in the first place: According to exit polling conducted by Edison Research, about one in four voters said the Supreme Court was the most important factor in their vote, and 56 percent of those voters backed Trump vs. 41 percent for Democrat Hillary Clinton.

For another, it sends a signal to Trump that the GOP’s conservative base expects him to make good on his promise to nominate reliably conservative judges. During the campaign, Trump released two lists of 21 total potential nominees. They include state Supreme Court justices, federal appeals court judges and one sitting senator — Mike Lee (R-Utah) — most of them active and well-known in conservative legal circles, such as the Federalist Society.

“This list is definitive, and I will choose only from it in picking future Justices of the United States Supreme Court,” Trump said in September.

Earlier this month, the JCN aired ads thanking Sen. Charles E. Grassley (R-Iowa), the Senate Judiciary Committee chairman, for keeping President Obama’s pick Merrick Garland off the court. Grassley allied with Majority Leader Mitch McConnell (R-Ky.) and most other Senate Republicans to blockade any Obama nominee in hopes that he might be replaced by a Republican. As the president-elect might put it, that bet paid off big league.

In the months after Scalia’s death in February, the JCN aired more than $5 million in ads in key states across the country. Carrie Severino, the group’s chief counsel and policy director, said Trump “made history” by issuing his lists of potential nominees and suggested that straying from them would constitute a significant betrayal.

“[M]any general election voters cast their votes for Trump because they believed his promise that he will nominate Supreme Court justices who will fairly apply the law and not make it up, or impose a personal or political agenda from the bench,” Severino said in a statement. “The President-elect promised to make America great again — one of the best ways to do that is to make good on his promise to select judges who will carry on the legacy of the late Justice Antonin Scalia, judges who will honor and respect the Constitution.”