Senate Republicans staged an unprecedented blockade of Barack Obama’s nomination to fill the US supreme court seat left vacant by the unexpected death of Justice Antonin Scalia. This gamble could have failed, allowing Hillary Clinton to nominate a younger and more liberal justice than Merrick Garland.

Instead, from their perspective, it was a huge success. Republicans will now maintain control of the court. And depending on how many nominations Donald Trump gets, very rightwing Republican justices could be in control of the supreme court for more than a generation.

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The first question arising from all this is what kind of justices Donald Trump will nominate. The answer to this question is actually straightforward: pretty much the same kind of justices any Republican president would nominate. Some anti-Trump conservative intellectuals have fretted that Trump cannot be counted on to nominate conservative justices, but there’s little basis for that belief. Trump’s proposed list of judges was a standard-issue conservative wishlist, and there’s no reason to think it doesn’t reflect how Trump will act in office.

And of course, while a Republican Senate is unlikely to be a very effective check on Trump’s worst excesses, it will be an effective check on any moderation in appointments. A Republican Senate rejected George W Bush’s nomination of Harriet Miers as insufficiently reliable or qualified, and they would do the same thing in the highly unlikely event that Trump nominated a justice who doesn’t come from the Federalist Society wishlist.

The best-case scenario for Democrats, then, is that Trump gets only one nomination. Replacing Scalia will not, in itself, transform the court. Scalia was a reliable conservative, and the moderate Republican Anthony Kennedy will remain the median vote. Replacing Scalia will still have some bad immediate effects, though – the court will now almost certainly act to cripple unions, for example. But at least Roe v Wade and the federal right to same-sex marriage will remain safe.

Trump could have a much longer-term impact on the court, however. Given how favorable the Senate map is for Republicans in 2018, he will almost certainly have a window to get nominees confirmed throughout his first term. One of the court’s Democratic-appointed justices, Ruth Bader Ginsburg, is an 83-year-old survivor of pancreatic cancer. Another, Stephen Breyer, is 78. Both might be on the court in 2021, but you wouldn’t want to bet too much on it.

And, frankly, it’s hard to avoid the conclusion that they acted irresponsibly by not resigning when Barack Obama still had a Democratic Senate before the 2014 midterms. It is very possible that this decision will mean that Ginsburg’s sterling legacy of advancing gender equality and civil liberties will be undone by her decision.

A great deal could also turn on how Anthony Kennedy, the 80-year-old moderate Republican, perceives Trump. Typically, one would expect a justice in Kennedy’s position to resign and allow a president from his party to choose his successor even if he’s physically able to remain on the job. It’s possible that Kennedy is disdainful of Trump’s brand of Republicanism and doesn’t want his landmark rulings on LGBT rights overruled. Or he may, like so many Republicans have, treat Trump as a normal Republican and allow him to pick his successor.

If Trump could appoint between two and four justices, the impact would be extraordinary. A very conservative Republican bloc would control the court, possibly for decades. A woman’s constitutional right to an abortion would be extinguished. The national right to same-sex marriage would also be likely to go. The civil liberties of citizens would be severely diminished. The rights of workers will be seriously curtailed, and American business will act with fewer regulatory constraints.

The next Democratic government would face a supreme court that takes a narrow view of federal powers. And by allowing money to swamp elections and vote suppression by state legislatures, a Republican supreme court would continue to tilt the political playing field in favor of the Republican Party.

Donald Trump might be president for only four years. But even that is probably enough time to produce a supreme court that would have a huge policy impact on American politics long after he has left office.