clarification: This editorial wrongly implied that Sen. Susan Collins (R-Maine) does not favor taking substantive measures after comments President Trump made Monday in a news conference with Russian President Vladimir Putin in Helsinki. In fact, Ms. Collins has spoken favorably about new potential sanctions on Russia and other measures.

PRESIDENT TRUMP on Tuesday tried to calm the wave of criticism that has pummeled him since his ignoble Monday news conference with Russian President Vladimir Putin in Helsinki. “I have full faith and support for America’s great intelligence agencies,” he said, a day after proving just the opposite. “I accept our intelligence community’s conclusion that Russia’s meddling in the 2016 election took place,” he continued, before extemporizing, “Could be other people also. A lot of people out there.” In Helsinki, he called the Justice Department investigation into that interference “a disaster for our country.”

Mr. Trump’s transparent effort at damage control — too little, too late, on the wrong continent — will not undo the damage he caused. Allies will believe his true feelings were revealed during his off-the-cuff remarks in Helsinki, not in the scripted backtracking he attempted after his countrymen found them contemptible — particularly because he could not even stick to the script.

Those who can undo some of the damage sit at the other end of Pennsylvania Avenue. Substantive, meaningful options are available. The question is whether Congress will move beyond tut-tutting and toward action that begins to restrain Mr. Trump.

On Tuesday, some lawmakers seemed stumped. “We can’t tell the president what to say. All we can do is make very clear that we disagree with the approach the president has taken,” Sen. Susan Collins (R-Maine) said, according to Vice News’s Alexandra Jaffe. “I think only the president can rein himself in,” Senate Judiciary Committee Chairman Charles E. Grassley (R-Iowa) said.

That’s not correct. Of course, senators can pass a resolution supporting U.S. intelligence professionals and making clear the United States and Russia’s gangster regime are not equally at fault for sour relations between the two countries, as Mr. Trump suggested before Mr. Putin on Monday. The gesture would send a message of sanity to allies and indicate that the Republican Party is not entirely a Trump personality cult.

But Congress could do far more than adopt resolutions.

U.S. intelligence officials have warned that Russia is likely to attack the U.S. democratic process again. Congress should therefore pass a bill requiring the application of specific and serious sanctions if the Russians are again caught interfering. It can also commit more to bolstering election security, as various panels have recommended since Russia’s 2016 intrusions.

Congress should require that Mr. Trump, immediately, and major presidential candidates, in the future, disclose their tax returns and other financial records, removing any suspicion that a president could be blackmailed by a foreign power.

Lawmakers could finally pass a bill protecting the Russia probe of special counsel Robert S. Mueller III, making it more difficult for the president to fire him. Until now, Senate Majority Leader Mitch McConnell (R-Ky.) has refused to bring that legislation up for debate. Congress also could limit the president’s power to impose counterproductive tariffs on spurious national-security grounds.

“There are a lot of us who understand what happened in 2016, and it really better not happen again in 2018,” Mr. McConnell said Tuesday. Are he and other Republicans prepared to back up those words?