Nancy Pelosi just might be speaker again someday if she turns “ethics” into the watchword of the Democratic minority and forces a lot of House floor votes.

She has a new opening to do it, thanks to a House Republican majority so tone-deaf and self-absorbed that it tried to open the Trump era by gutting the Office of Congressional Ethics.

Sure, Pelosi had a bunch of defections in the House speaker vote Tuesday, and, sure, district lines are drawn to give Republicans a mortal lock on the majority.

But there’s one issue — and only one issue — that can create an electoral earthquake: Ethics.

Pelosi knows that.

Back in 2006, when she was minority leader and Republicans held the White House and both chambers of Congress, Pelosi’s promise to drain the swamp in Washington got a big, 11th-hour boost from the Mark Foley page scandal.

Speaker Dennis Hastert had ignored it. Republicans were thrown out on their ears, and Pelosi became the first female speaker of the House and the first Democrat to hold the gavel since Newt Gingrich’s 1994 revolution. Gingrich had been pushed out after his own ethics scandal, and the pursuit of an impeachment of President Bill Clinton contributed to a poor Republican showing in the 1998 midterm elections.

House Republicans pulled their hands back from the burning stove-top Tuesday, but not before they left their fingerprints all over an effort to loosen oversight of congressional ethics.

That should give everyone pause, particularly Republican voters. It was enough to get The Donald to pull out his smartphone and tweet a rebuke.

Of course, the first vote, taken behind closed doors at night on a federal holiday, is objectionable because Trump campaigned on cleaning up Washington. And it took a lot of chutzpah for Republican lawmakers to whine about the reputational damage of ethics charges that turn out to be unfounded.

Where were they when their convention chanted “lock her up” at Hillary Clinton? Beyond that, the American public has a right to be angry about the effort to remove a layer of accountability from the congressional ethics process.

But the real reason that Republicans should be worried, and that Democrats should be excited, is that it was such unbelievable political malpractice.

On the heels of winning control of the White House and both chambers of Congress for the first time in a decade, and having made the case that the other side was corrupt, the very first priority of House Republicans was to make it easier for lawmakers to abuse the public trust.

That’s talking-point gold for Pelosi and her Democrats. Presumably, Republicans changed course not because they thought they were wrong but because the public backlash threatened to sink the package of rules for governing House floor action.

Before Trump tweeted, members of his team had defended the decision. No one seemed to think it was wrong. And even The Donald took a shot at the ethics office — “as unfair as it is” — in his tweet admonishing House Republicans to focus on health care, tax reform and other issues before ripping up the Capitol ethics regime.

To be fair, members on both sides of the aisle hate the OCE because it’s one of the few entities not under their control. And, at times, it has been a little hyperactive. An earnest attempt to reform it might have been met with cheers from Democrats as well as Republicans.

But instead, the GOP went for the jugular, and, in doing so, revealed a willingness to repeal rather than enhance ethics standards.

Pelosi would be smart to arm herself and her caucus with an ethics message now.

She and her fellow Democrats could write hundreds of ethics-reform bills aimed at members of Congress, executive-branch employees, judges and federal workers. They could introduce them and hold daily press conferences about the Republican leadership bottling the bills up in committee. And Democrats could use new Appropriations amendment rules as a vehicle for putting Republicans on the record over and over again on more narrowly tailored ethics proposals.

Pelosi could even reward members who come up with the most and best ideas for reforming government. She could also take to the floor regularly and use the mechanism of “privileged” resolutions to force uncomfortable ethics votes on the GOP majority. That is, there are a lot of ways for Pelosi to cast the GOP as the party that paid lip service to reform and her own party as the one that put its money where its mouth was.

Despite his politically savvy tweeting on Tuesday, Trump has set a standard for conflicts of interest at such a low level that it will invite corruption at all levels of government — including the branch just down Pennsylvania Avenue from his new weekday home.

Just look at what House Republicans tried to do on Day One of the new Congress.

If that’s how they’re going to behave, and if Pelosi can remember the way she attacked them in 2006, their majority will be short-lived.