One thing we fought for that’s worth defending is a fairer, more open and more productive Senate. We changed the Senate rules to guarantee a president’s nominees a simple-majority vote, and declared that a president’s nominees should not be stymied with procedural hurdles and a requirement for supermajority votes. (Supreme Court nominations still have this requirement.)

We declared that the changes should apply regardless of which party was in the White House, because fair votes are what democracy is all about. I doubt any of us envisioned Donald J. Trump’s becoming the first president to take office under the new rules. But what was fair for President Obama is fair for President Trump.

Moreover, the rule change has been a victory for those who want to see a functioning, open and transparent Senate. It allowed Mr. Obama’s judicial nominees to receive the just consideration they deserved. Without the rule change, Republicans would have been able to hold open three seats on our nation’s second highest court, the District of Columbia Circuit Court, until the next Republican administration. The judges we confirmed to those seats will loom large in the years to come. In 2014 alone, the Senate confirmed 89 Circuit and District Court judges, more than for any year in two decades.

The rule change was consistent with the history of the Senate, which has continually evolved when faced with new challenges. Historically, the only way to reject nominees to cabinet posts, which are not lifetime appointments, has been by a simple-majority vote. Moreover, the supermajority threshold for bills and nominations is not in the Constitution, nor was it in the original Senate rules.

From George Washington to George W. Bush, only 68 presidential nominees had been filibustered. Senate Republicans took obstruction to a new level, filibustering 79 of Mr. Obama’s nominees in just four years. By removing such procedural ploys, the rule change puts the debate over nominees out in the open. Senators have to answer a simple question: Should a nominee be confirmed, or not? Nominees are now guaranteed a floor vote.

With Republicans holding a slim majority, Democrats have a fighting chance at winning every debate. To be sure, persuading a majority of the Senate to your side is harder than blocking a confirmation on a procedural vote. But it is also fairer.

When Democrats pick their fights next year, they can do so knowing that, win or lose, they will be debating in a Senate that we made more open and more transparent. If Democrats stand for what they believe in, they will find that trusting the courage of their convictions while out of power will empower them to accomplish great things when the pendulum swings back, as it always does.