Hillary Clinton has the capacity to do something that almost never gets discussed in the campaign: change the ideological landscape of the federal judiciary for a generation. It could be one of the defining features of her legacy.

In part, that will be a consequence of getting to fill the Supreme Court vacancy left open by Antonin Scalia — creating the first progressive Supreme Court majority in decades and opening the door to much more expansive efforts at progressive legal advocacy.

But it more subtly reflects a Clinton administration’s likely impact on lower courts.

This is important because the vast majority of cases, after all, never make it to the Supreme Court. But like-minded District and Appeals Court judges will push any new liberal precedents forward and lead the evolution of big-picture constitutional doctrine in its post-Scalia direction.

An odd confluence of circumstances — the elimination of the filibuster for judicial nominees followed by the 2014 midterms leading to an utterly intransigent GOP Senate majority — in President Barack Obama’s second term means that a Clinton administration and a Democratic Senate will face an unusually large number of vacancies and have an unusually easy time filling them.

That will let Clinton staff the lower courts with a big new cohort of judges who’ll be systematically more sympathetic to criminal defendants, labor and environmental plaintiffs, and government regulators — transforming the federal judiciary back into a powerful prop of progressive governance for years to come.

Nuclear winter on the judiciary

Judicial nominations in Obama’s first term had an essentially familiar pattern to them, albeit in an extreme and heightened form. Obama was president, and Democrats controlled the Senate. Republicans largely agreed that, in some sense, this meant he was entitled to fill judicial vacancies with Democratic Party appointees.

But they didn’t have to be happy about it. Delaying tactics were routinely put in place to make filling vacancies an arduous endeavor. And the filibuster rule requiring 60 votes to move on any piece of Senate business served as a powerful practical check on Obama’s freedom of action. Many judges got confirmed, but it was slow, grinding work, and any small vetting problem was enough to consign a nominee to filibuster doom. More outspokenly liberal nominees were also rejected via filibuster, while more moderate ones were allowed to advance to preserve the norms of the system.

This largely came to an end in Obama’s second term when an escalating game of partisan ping-pong came together to lay the groundwork for a coming Clinton confirmation boom:

With the Democratic Senate margin reduced, Republican obstruction grew bolder and confirmations slowed to a trickle. Harry Reid and Senate Democrats deployed a long-discussed “nuclear option” — essentially using a majority vote to change the rules — to prevent filibustering of judicial nominees, leading to a brief spurt of confirmations. Republicans won control of the Senate in the 2014 midterms, and responded to Reid’s nuclear call by shutting down confirmations altogether.

That means that if Clinton and Democratic Senate candidates win in November, they’ll have an unusually easy time filling vacancies thanks to the nuclear option, and an unusually large number of vacancies to fill thanks to the near-total confirmation blockade during Obama’s final two years.

Clinton’s lower court opportunity

The basic picture of a president facing an opposition Senate in his final two years in office merely repeats the circumstances faced by Presidents Reagan, Clinton, and Bush. But as the Brookings Institution’s Russell Wheeler notes, “Similarities end with confirmations in that same period.”

As of April 2016, he wrote, “district vacancies have almost doubled” to 72 since the 2014 midterms, whereas in “in the comparable time periods for Reagan and Bush, district vacancies declined slightly; for Clinton they increased, but came no where near doubling.”

The upshot is that right now 10 percent of the seats on the federal district court benches are vacant. That number is sure to rise between now and November, both in light of seven currently announced retirements and more broadly because more judges will step down once they know the outcome of the election. And on federal appeals circuits there’s currently a 7 percent vacancy rate.

Senate Republicans could have used their leverage over the process to force Obama to fill those seats with moderate nominees. They’ve chosen instead to block everything — gambling on winning in November and having a like-minded president fill them with like-minded judges.

Even as Republican victory has started to look less likely, the party’s internal dynamics have prevented them from shifting to a more compromising posture. And due to the exercise of the nuclear option years earlier, a post-election GOP Senate minority will have no power to stop Clinton from filling the seats as she sees fit.

An opportunity for judicial progressives

The opportunity is particularly exciting to liberals. In part because of the polarized landscape, Clinton will have even less reason than Obama or her husband did to push back on activist pressure to nominate outspoken progressives. Every once in a while, Obama did pass a boldly liberal nominee over to the Senate, typically just to see the nomination killed by Republicans. That’s what happened to Goodwin Liu, for example, in a particularly noteworthy case.

But the nuclear crisis changes the dynamics around this. In a recent Politico story on Obama-era nomination battles, Michael Grunwald recounted the improbable story of how Nina Pillard became a judge on the highly influential DC Circuit:

Pillard, an outspoken feminist litigator and law professor, did not fit the Obama pattern of low-profile nominees with minimal paper trails. In fact, White House sources say they never expected her to get confirmed. They figured she would be a sacrificial lamb, a scalp Republicans could claim while confirming Millett, an uncontroversial appellate lawyer, and hopefully Wilkins, an African-American judge who had been confirmed unanimously to the D.C. district court in 2010. But the Republicans decided to filibuster all three nominees, to stop Obama from shifting the balance of the court. They didn’t think they’d pay a political price, since most voters ignore lower-court nominations, while grass-roots conservatives who loathe Obama tend to pay closer attention.

Republicans simply assumed that the old bulls of the Democratic Senate caucus, like Vermont’s Pat Leahy, would stop Reid from pulling the trigger on the nuclear option. But the Republican blockade on the DC Circuit ended up, for complicated legal reasons, preventing Obama from filling important vacant executive branch posts on the National Labor Relations Board and the Consumer Financial Protection Agency. That led Democrats to go nuclear, and meant that Pillard suddenly went from unconfirmable sacrificial lamb to federal judge.

Clinton won’t nominate a full slate of Pillards and Lius. But she will face pressure from progressive groups to lean more in that direction, and the altered political context means there will be little pragmatic case against picking them. Liu’s wife, by the way, is Ann O’Leary, who served as legislative director in Clinton’s Senate office, is also one of the heads of the Clinton transition team whose job it will be to present the president-elect with a set of names to put forward.

Nothing better to do

Last but by no means least, we can expect a substantial judicial legacy from Clinton in part because she’ll be in the unusual position of not having all that much else to do with her time. It’s not inconceivable that she will get some legislating done even if she has to deal with a House Republican majority. But anything that happens under those circumstances would necessarily be the product of long, quiet negotiations and wouldn’t thrill the hearts of activists in the base of Clinton’s coalition.

She will, like any new president, face pressure to deliver something for the people who put her in office. But between eight years of activity from the Obama administration and a likely GOP majority in the House, the scope for both executive and legislative action will be limited.

Appointing judges who’ll champion the causes of environmentalists, labor unions, racial justice activists, and others is something Clinton not only can get done but will actually have more scope to accomplish than any recent president.

A new era of progressive lower-court judging probably isn’t going to be at the front of anyone’s mind when considering their options in 2016, but when we look back on what’s been accomplished in 2017, it’s likely to be near the top of the list.