The Constitution of the United States establishes a system of checks and balances. Unfortunately for the republic, this system was rendered meaningless by House Speaker Paul Ryan and Senate majority leader Mitch McConnell during the first two years of Donald Trump’s presidency. The legislative branch did not temper the worst excesses of the executive branch. It sustained and enhanced them. Trump wanted this arrangement to continue.

On Tuesday, however, the American people chose a different arrangement. Though they kept the Senate in Republican hands—with an enhanced majority for McConnell’s caucus—voters elected a House of Representatives that will be controlled by the Democrats.

As it became clear that her party would take charge of the chamber following the most contentious midterm election in modern American history, House Democratic leader Nancy Pelosi of California announced that “Today is more than about Democrats and Republicans. It is about restoring the Constitution’s checks and balances to the Trump administration.”

That was a sweeping statement. And rightly so. What has taken place is epic in character, and strikingly consequential for the future of an American experiment that has since 2016 been battered by Trump and his partisan allies.

The size of the Democratic majority will be decided by the final counts and recounts. But the fact of the shift that the voters initiated on Tuesday restores a measure of balance to Washington after two years of absolute domination by a Republican Party that has been remade in Donald Trump’s image. The consequences of this development for Trump were summed up by Maryland Congressman Elijah Cummings, the Democrat who will take charge of the powerful House Oversight and Government Reform Committee.

A lawyer, who has served in the House for more than two decades, Cummings spoke of his new duties in starkly constitutional terms. “I want to look at all the things the president has done that go against the mandates of our founding fathers in the Constitution,” he declared. “We need accountability, transparency, integrity, and honesty from this administration.”

“Right now, we have a president who is accountable to no one,” Cummings told CNN. That, he explained, is about to change.

How much it changes is an issue of great concern to grassroots activist across the country, who have from the first days of Trump’s tenure argued that Congress must address this president’s blatant disregard for his oath of office and the rule of law. “The change in control over the U.S. House of Representatives marks a significant step forward, but it will not, on its own, end Donald Trump’s corrupt and dangerous reign,” says Tom Steyer, the founder of NextGen America who has poured energy and resources into organizing the national Need to Impeach movement.

“The American people have voted for real change, and it’s critical that these new representatives recognize this will only come with a true political reckoning for the corruption, self-dealing, and lawlessness exemplified by Mr. Trump,” Steyer said after if became clear Democrats would take the House. “He cannot be permitted to continue to break the law with impunity.”

The oversight committee will not be alone in reasserting the system of checks and balances. Incoming House Judiciary Committee chairman Jerry Nadler (D-NY) says Trump is “going to learn he’s not above the law.” The extent to which Trump will be held to account depends, at least to some extent, on the conclusions that are drawn from special counsel Robert Mueller’s probe into Russian interference in the 2016 presidential election. Nadler has been an ardent defender of the Mueller investigation. And he is well aware of the issues it could raise for Trump and for Congress.

The incoming Judiciary Committee chair told Politico last year, “If you are actually going to remove a president from office, you are in effect nullifying the last election. Certainly the people who voted for him will think you’re nullifying the election. It’s OK to do that. It may be necessary to do that—as long as you have persuaded a sufficient fraction of the president’s former supporters, the people who voted for him, that you have to, that it’s necessary.”

Nadler, like Cummings, is a senior member of the House. He will not rush to judgment. But he has said that “we are going to have to do something to provide a check and balance, to protect the rule of law and to protect the legitimacy of one of our most important institutions.”

In other words, the oath that key members of the House swear to “support and defend the Constitution of the United States against all enemies, foreign and domestic” will now be more than an empty promise.