The old saying that elections have consequences was hammered home Wednesday when Supreme Court Justice Anthony M. Kennedy announced he would retire — handing President Trump a chance to appoint a second justice in a little more than a year and potentially cement a conservative majority for a generation.

The decision hit like a thunderbolt in Washington.

Just as Democrats dreamed about reining in Trump by taking control of the House this fall, the president is poised to again wield one of the most powerful levers available to him.

Kennedy's departure is "the most consequential event in American jurisprudence at least since Bush v. Gore in 2000 and probably since Roe v. Wade in 1973," said Jack Goldsmith, a Harvard Law professor who once clerked for Kennedy. Writing for the Washington Post, he added, "His departure leaves the future of U.S. constitutional law entirely up for grabs."

The prospect of a fight over the future of the high court added tension to an already raging public debate over Trump, the looming congressional races, and widening cultural divides.

Trump on Wednesday vowed to nominate a replacement quickly, working off an existing short list of candidates. Senate Majority Leader Mitch McConnell immediately went to the Senate floor and said the GOP-controlled chamber would act on a replacement this fall.

The stakes for a single Supreme Court seat have been made clear in recent days, when a series of 5-4 decisions have upheld conservative priorities in cases dealing with Trump's travel ban, abortion, and labor unions. Other recent 5-4 decisions upheld a Republican plan to purge voter rolls in Ohio and political district boundaries in Texas that critics argued discriminated against minorities.

If Trump replaces Kennedy — who sometimes sided with the court's liberal justices and swung major decisions their way — with a reliable conservative, the right could hold a solid majority for a generation to come.

That could very well end up as the most consequential result of a presidency effectively decided by about 80,000 votes in Pennsylvania, Michigan, and Wisconsin, Trump's combined margin in three swing states that provided critical Electoral College votes.

Democrats immediately feared the worst.

Kennedy had sided with liberal justices in decisions that protected abortion and established a national right to same-sex marriage.

"I'm worried about Roe v. Wade," tweeted Sen. Jeff Merkley (D., Ore.).

With Kennedy's retirement, "reproductive rights and the newly  gained rights of LGBTQ Americans lie in the hands of an extremist president," Sen. Bob Menendez (D., N.J.) said in a statement. "I call upon the American people to rise up, make your voices heard, and tell the Senate that you will not accept another extreme Supreme Court justice."

Sen. Patty Murray (D., Wash.) tweeted that "Justice Kennedy's retirement comes at a pivotal point in our nation's history, when so many of our values are under attack by a president who has spent every day in office testing the limits of our Constitution."

Democrats are still seething that Trump had even filled one Supreme Court seat. His first pick, Neil Gorsuch, is on the court only because McConnell, in an unprecedented obstruction, blocked President Barack Obama's nominee to fill a vacancy for more than nine months in 2016.

McConnell argued that in a presidential election year, voters should get a chance to weigh in on such an important appointment. Merrick Garland, Obama's pick to replace Justice Antonin Scalia after Scalia died, never got a hearing. When Trump won the election, he claimed the right to fill the seat.

For many Republicans, Trump's support for conservative jurists was enough reason to overlook concerns about his personal conduct and support him over Democrat Hillary Clinton.

In choosing Gorsuch, Trump named a conservative to replace a conservative. Now he has the opportunity to replace a swing vote with yet another voice from the right. (Among those who might be in the mix: Pittsburgh's Thomas Hardiman, a Third Circuit Court of Appeals judge who was a finalist when Trump made his first Supreme Court nomination.)

Democrats and political pundits were quick to remind McConnell of his stand in 2016.

"Millions of people are just months away from determining the senators who should vote to confirm or reject the president's nominee, and their voices deserve to be heard now, as Leader McConnell thought they deserved to be heard then," said the Democrats' Senate leader, Chuck Schumer. "Anything but that would be the absolute height of hypocrisy."

McConnell told reporters at the Capitol that the blockade applied to Supreme Court nominees in presidential election years — not midterms like the elections in 2018.

Democrats have few tools with which to stop a Trump nominee.

Republicans, escalating decades of judicial wars, already invoked the "nuclear option" in the fight over Gorsuch, gutting the minority party's power to block Supreme Court nominees. About the only hope for Democrats is to try to persuade some Republicans to turn on a Trump nominee, given the GOP's narrow two-seat majority and the continued absence of Sen. John McCain (R., Ariz.).

But there are 10 Democrats from states Trump won, and they, too, will face pressure to break ranks and vote for the president's nominee. Three voted for Gorsuch.

Now comes an even more heated political moment, with even greater consequences.