Daniel W. Drezner is a professor of international politics at the Fletcher School of Law and Diplomacy at Tufts University and a regular contributor to PostEverything.

Susan E. Rice was national security adviser in the Obama administration. (AP)

There’s a lot of talk about the erosion of political norms going around in 2017. Today might be the day that the GOP majority ends the Senate filibuster to ensure the confirmation of Neil Gorsuch to the Supreme Court. This is the inevitable endpoint to the “parliamentary arms race” caused by increased polarization. Of course, as Sarah Binder points out in The Post’s Monkey Cage blog, one of the problems with this dynamic is that no one agrees on who started it:

Partisans disagree about who is to blame for bringing the Senate to the nuclear brink. Republicans fault Democrats for stoking the war by filibustering George W. Bush’s judicial nominees and going nuclear in 2013 over executive and lower court appointees. Democrats blame Republicans for their reflexive opposition to President Obama’s nominees, including the GOP’s unprecedented refusal to consider Obama’s Supreme Court nominee, Merrick Garland.

The increasing intransigence of Democrats to anything remotely resembling cooperation with Trump is also causing a few tut-tuts in Punditland.

As someone who’s been a fan of these norms for his adult life, I’m more concerned about the norms that are eroding in the national security arena. In Lawfare, Benjamin Wittes and Jack Goldsmith point out that acting against one’s own partisan interests is one of the big things that makes the system work. Consider the Russia investigations:

The key here is to have credible bipartisan voices to authenticate Comey’s judgments, and to discern and confirm the facts where he does not report them. We need voices who can look at the evidence and call it like they see it, even when it goes contrary to political interest. In Washington, after all, actions contrary to political interest are always the most credible, and often the only credible, actions.

John McCain, Lindsey O. Graham, Marco Rubio, and other Republicans who acknowledged the evidence of Russian hacking and contradicted the President on it played a hugely important role a few months ago. And today, likewise, only (or primarily) Republicans can remove the sting of the President’s charge that the Russia investigation is baseless or biased against him. And only (or primarily) Democrats can speak with credibility if it turns out that some of the investigative techniques used in the Russia matter were, as the president has charged, inappropriate or if it turns out that it was Obama administration officials who leaked FISA materials.

For Republicans who think that Democrats haven’t done this at all during the Trump presidency, remember Rep. Adam Schiff’s (D-Calif.) endorsement of the laptop ban from a few weeks ago.

Of course, short-term partisan interests are pretty powerful. Whichever side is in power will be tempted to violate a norm to achieve some short-term interest without thinking about the long-run consequences.

Which brings the hard working staff here at Spoiler Alerts to President Trump, two words I still cannot type in sequence without shaking my head in disbelief.

A big reason for all the congressional Russia probes is that Trump tweeted something stupid about former president Obama and refused to back down. Today he crossed another line in an interview with the New York Times’ Maggie Haberman and Glenn Thrush:

President Trump said on Wednesday that Susan E. Rice, the former national security adviser, may have committed a crime by seeking to learn the identities of Trump associates swept up in surveillance of foreign officials by United States spy agencies, repeating an assertion his allies in the news media have been making since last week.

Mr. Trump gave no evidence to support his claim, and current and former intelligence officials from both Republican and Democratic administrations have said they do not believe Ms. Rice’s actions were unusual or unlawful. The president repeatedly rebuffed attempts by two New York Times reporters to learn more about what led him to the conclusion, saying he would talk more about it “at the right time.”

The allegation by a sitting president was a remarkable escalation — and, his critics say, the latest effort to change the story at a time when his nascent administration has been consumed by questions about any role his associates may have played in a Russian campaign to disrupt last year’s presidential election.

This is a pretty extraordinary claim. Most national security experts have stressed that what Rice did was neither illegal nor unusual. Even Eli Lake, the BloombergView columnist who has made the strongest case that the Obama administration had improperly handled intelligence, wrote that Rice did nothing illegal.

Trump’s supporters, small in number though they may be, are nonetheless gleeful at this misdirection:

My hunch is that the Rice story will have a decent half-life, because Susan E. Rice and television have never mixed terribly well. Her own efforts at defense will be likely to generate additional controversies and news cycles. That said, it’s highly unlikely that anything untoward will be found.

No, what concerns me about this story is whether Trump has really thought this through. One of the few political norms that has endured into the 21st century is that new administrations are reluctant to prosecute high-ranking officials from past administrations for bad behavior. During the 2016 presidential campaign Trump promised to prosecute Hillary Clinton for Benghazi but backed down from that promise during the transition. When Barack Obama replaced George W. Bush, he decided not to prosecute any Bush officials for anything related to the torturing of prisoners in the War on Terror. Writing in Slate in 2014, Eric Posner explained why Obama made that decision:

Obama’s best argument for letting matters rest is the principle against criminalizing politics. This is the idea that you don’t try to gain political advantage by prosecuting political opponents — as governments around the world do when authoritarian leaders seek to subvert democratic institutions. Of course, if a Republican senator takes bribes or murders his valet, the government should prosecute him. But those cases involve criminal activity that is unrelated to the public interest. When the president takes actions that he sincerely believes advance national security, and officials throughout the government participate for the same reason, then an effort to punish the behavior — unavoidably, a massive effort that could result in trials of hundreds of people — poses a real risk to democratic governance.

Obama’s problem is that if he can prosecute Republican officeholders for authorizing torture, then the next Republican president can prosecute Obama and his subordinates for the many questionable legal actions of the Obama administration.

The more that Trump says that members of the Obama administration committed high crimes and misdemeanors, the more he will criminalize politics. That kind of rhetoric will no doubt play well with his base, and stoke the partisan fires for a bit longer.

Much like Trump’s proposed EPA cuts, however, the long-term effects will be devastating. The ongoing polarization of American politics suggests that the next Democratic president will need to play to his or her base just as much as Trump is doing right now. Trump’s provocative rhetoric creates a powerful precedent for the next Democratic president to investigate former Trump officials for crimes as well. And given who the president is and how this administration has been run, it seems like a target-rich environment for any decent prosecutor.

I’m sure that Trump thinks that, as president, he is above the law. Eventually, however, he’ll be an ex-president. He should remember that before violating more political norms.