A new front is opening in the war between Democrats and Republicans in this election year. By choosing Merrick Garland, a centrist judge on the District of Columbia Court of Appeals, for the Supreme Court, President Barack Obama is playing right into it.

Having decided that they must await the outcome of the presidential election before filling the Supreme Court seat left vacant by the death of the ultraconservative Antonin Scalia last month, Republicans today find themselves in a position that is uncomfortable, if not outright ridiculous.

On Mr. Obama’s part, the choice is a clever one because 63-year-old Merrick Garland is a man whose qualities have been praised from all sides since his appointment to the D.C. Court of Appeals in 1997. A steadfast moderate, he is clearly a consensus candidate. But as everyone knows, there are some years when the American political class cannot reach even the most minimal compromise.

Once again on Tuesday, always ready to push their obstructionist logic to absurd limits, the Republican majority in Congress reiterated that it was out of the question that the Senate, which is responsible for approving the president’s choice, begin the vetting procedures. Republicans defended themselves by arguing that this was too important of a process to be undertaken in an election year. But this defense doesn’t hold water, since in the past, as U.S. media have confirmed, 14 justices have been named to the Supreme Court during election years.

Obviously, the stakes are high. The U.S. Supreme Court plays a highly political role. Its nine justices, appointed for life, have repeatedly been called upon to intervene in society’s great debates. Their decisions have significant social impact. Currently, following Antonin Scalia’s death, the Court is split down the middle, with four conservative justices and four progressive justices. Down the middle, although not necessarily completely so: After all, one of the so-called conservative members, Anthony Kennedy, appointed by former president Ronald Reagan, tipped the scales last year in favor of gay marriage. With that said, if Mr. Garland did join the Supreme Court, the Court’s composition would be the most “liberal” of the past 50 years.

The Republican strategy is clear: Block the nomination of a ninth justice until the November elections in the hope that they will win the presidential election and retain control of the Senate, thereby allowing them to install a notably more conservative choice in the Supreme Court.

But to refuse to weigh in on Mr. Garland’s candidacy out of paralyzing partisanship is to sin through a grossly anti-democratic reaction. They are showing how far they have slid to the right, pulled by the ultraconservative Freedom Caucus in the House of Representatives, a group with close ties to the evangelical senator from Texas, Ted Cruz, Donald Trump’s main rival in the race for the Republican nomination. Trump, outsider that he is, is on this subject in tune with the Republican majority: If he becomes president — and anything is possible — the power will be vested in him to choose the ninth justice.

As it happens, it’s all a story of electoral math. On their side, the Democrats are betting that this new battle will help them mobilize the left, and that, this coming autumn, this issue will make Republicans look so bad that they will lose their Senate majority. It’s clever, but it’s also expecting a lot.