There is likely no political issue more important to either side of the ideological spectrum than who controls the Supreme Court.

Rumors are building that another justice is going to retire this summer. The odds-on favorites are two members in their 80s: Ruth Bader Ginsburg, a liberal justice, and Anthony Kennedy, the notorious swing vote.

If either retire, President Donald Trump’s next nominee could determine the balance of the court for decades—and the fight over that justice will be a battle royale.

But as enticing as such prospects may be, is it possible that Trump’s appointments to lower courts are just as important?

The often overlooked reality is this: Whether it’s blocking travel bans or redefining marriage, the Supreme Court only hears cases that lower courts have already heard and voted on. And many of those cases never even reach the Supreme Court.

Take a look at these numbers.

There are 94 federal district courts across the country with 670 judges. In 2014, the number of cases filed in those courts was over 390,000.

Then there are the all important 13 courts of appeals with 179 judges. In 2014, the number of cases filed in those courts was over 55,000.

Now consider the fact that each year, the Supreme Court only chooses to hear approximately 70 cases.

Needless to say, from property rights and environmental regulations to state laws on abortion and voting rights, the vast majority of legal cases are decided by judges you’ve never heard of.

And just like the Supreme Court, federal judges are lifetime appointments.

Before President Barack Obama took office, only one, just one of the 13 courts of appeals—the 9th U.S. Circuit Court of Appeals—was considered liberal. Following Obama’s two terms, nine of the 13 are now controlled by Democrat appointees.

And the rulings of one circuit court can make a huge difference. For example, the Virginia-based 4th U.S. Circuit Court of Appeals went from reliably conservative pre-Obama to reliably not conservative once Obama was able to appoint four justices to its bench.

Over the past year, that appeals court overturned North Carolina’s voter identification law and sided with a transgender teenager over a battle to use a boys’ restroom.

In 2014, it was the 4th Circuit that upheld the legality of tax subsidies under Obamacare—it was that case, King vs. Burwell, that the Supreme Court then took up and confirmed.

And it was the 4th Circuit that just last month upheld a Maryland district judge’s ruling blocking Trump’s executive order suspending travelers from certain countries.

One could say that Obama got a lot of bang for his policymaking buck with his four appointments that flipped the judicial philosophy of that court.

This is why, despite all their other actions, a president’s judicial nominees may be where they make their biggest long-term impact.

And, this is why, today, with over 120 vacancies scattered across the federal courts, Trump has the opportunity to shape the judiciary—and therefore the third branch of government’s impact on society—for years to come.

Based on the approximately 20 such nominees Trump has sent to the Senate thus far, conservatives should be encouraged.

Two of his appeals court nominees come from the list of 21 Supreme Court contenders he published before the election—all of which conservative legal experts considered excellent candidates.

Another nominee is a former law clerk to the late Justice Antonin Scalia.

And many of his nominees are in their 40s, which means, if confirmed, they will be influencing the federal courts for the next 30 years.

Most of them will never become household names but to a great extent, it will be these judges who determine which liberties Americans enjoy—and which ones they don’t.