For the most part, Congress abides by an unwritten rule: Don't do something that could set you up for a fight with your own party, especially your own president, unless you absolutely have to.

That's what makes a series of sanctions against Russia that the House passed on Tuesday so remarkable: It sets a Republican Congress directly up against a Republican president. And it's the clearest statement yet that Congress doesn't believe President Trump can or will effectively respond to the threat Russia poses.

“This is why this bill exists, is they don't trust the administration to do this right,” said Olga Oliker, director of the Russia and Eurasia program at the Center for Strategic and International Studies.

The bill, which passed the House by a 419 to 3 vote, imposes new sanctions on officials in Russia, Iran and North Korea. Notably, the legislation will prevent Trump from lifting some of those sanctions on his own, reported The Post's Mike DeBonis and Karoun Demirjian. The Senate could approve the package by the end of the week, and Trump will either be forced to sign it or get in a veto standoff with Congress. Margins like the one in Tuesday's vote show that's a standoff Congress could win.

The Russia sanctions are retaliation for Russia's alleged meddling in the U.S. presidential election. These will be in addition to sanctions President Barack Obama issued on his way out the door, kicking Russian “diplomats” out of Washington and seizing Russia-owned compounds in the United States.

If Congress thinks Russia needs more punishment, it's pretty obvious why they aren't confident Trump will do it.

The White House has said it's not opposed to sanctions, but it's been wishy-washy on what those would be. Also, the White House's official statements don't match with the president's actions. Trump has refused to acknowledge the overwhelming conclusion of U.S. intelligence officials that Russian President Vladimir Putin ordered Russia to try to influence the U.S. election to hurt Hillary Clinton and help Trump win. He appears to be considering firing his attorney general after complaining about the Justice Department investigation into Russia's actions and any possible help from the Trump campaign. He's considered giving the diplomatic compounds back to Russia.

A sizable majority of Congress has a polar opposite view on  how to handle Russia and decided to take things in its own hands. An initial version of these sanctions passed the Senate 98-2, and this version is expected to pass the House with at least a two-thirds (read: veto-proof) majority.

That's a remarkable demonstration of unity from a Congress that has shown exactly none of it lately. Tying Trump's hands on Russia is one of the only things Congress can agree on right now.

“There's a lot of stuff they'd rather be doing,” Oliker said, “and that they're much better equipped to deal with. But in the face of an administration that seems to be having a very difficult time articulating its foreign policy, members of Congress have felt they have little choice but to take foreign policy into their own hands.”

From a diplomatic perspective, it's not ideal for Congress to levy sanctions against foreign governments or officials. Both Congress and the president have the power to do so, but the White House's sanctions power is much more nimble. Trump can institute or lift them with the wave of a pen. It's a flexible carrot-and-stick approach and more in line with the nuanced way diplomacy works, Oliker said.

When Congress issues sanctions, they tend to stay in place for a while. A majority of lawmakers in both chambers to agree to them, then they are signed by the president. The same process has to happen to reverse them.

The last time Congress forced a president to impose sanctions against Russia was in 2012, when a Republican Congress forced President Barack Obama to impose sanctions against Russia with the Magnitsky Act.

The Magnitsky Act was put in place in retaliation for the human rights abuses suffered by Russian lawyer and auditor Sergei Magnitsky, who had uncovered a financial corruption scheme involving the Russian government. It originally blocked 18 Russian business executives and government officials from entering the United States and froze assets in U.S. financial institutions. And if it sounds familiar, it's allegedly one of the reasons a Russian lawyer set up a now-infamous meeting with Donald Trump Jr. during the campaign.

Anyway, in 2012, the Obama administration wanted a different set of '70s-era sanctions against Russia repealed. The Congress, then split between a Democratic-majority Senate and Republican-controlled House, basically repealed those and attached the Magnitsky Act. Then too, the message was: We don't trust you to be as tough on Russia as we want you to be.

Congress is saying the same thing to Trump today, only with an extra layer of political intrigue. Republicans are in control of Congress, so they decide which bills get a vote in either chamber. Thus they're primarily responsible for sticking it to Trump on Russia.

Republicans in Congress and Trump have mostly agreed on the broad strokes of policy: Repeal Obamacare, crack down on illegal immigration, end federal grants to Planned Parenthood.

But when it comes to getting tough on Russia, even Republicans in Congress don't trust their president.