President Donald Trump signed an executive order last week promising to punish anyone attempting to meddle in U.S. elections, including with “measures that could be capable of devastating an interfering country’s economy,” according to an administration description.

For a presidency marked by an inconsistent stance on Russia, it was yet another shift in tone. That inconsistency explains why this warning shot against Russia and other foreign adversaries, while welcome, is insufficient. Congress also should act.

The executive order charges the U.S. intelligence community with determining whether foreign entities — people, organizations, governments — have tried to interfere, either by direct cyberattacks on election infrastructure or by spreading propaganda. Findings would be forwarded to other agencies, which would apply initial automatic sanctions blocking any assets that bad actors have under U.S. jurisdiction. The Treasury Department could apply further sanctions of varying bite, calibrated to the severity of the intrusion.

The order gives the president and his top lieutenants much discretion; it would be up to them whether to go beyond the bare minimum of the automatic sanctions. Deterrence is the best defense against future meddling. Eliminating all vulnerabilities in the nation’s electoral infrastructure is impossible.

The most effective policy would involve a credible warning of massive retaliation. But credibility is in short supply for this administration, particularly after Trump’s obsequious performance before Russian President Vladimir Putin in Helsinki.

There are two bipartisan Senate proposals that, if passed, would send a stronger message. The bills — one shepherded by Sens. Marco Rubio, R-Fla., and Chris Van Hollen, D-Md., the other by Sens. Lindsey Graham, R-S.C., and Robert Menendez, D-N.J. — would insist on tougher automatic sanctions, such as on the sovereign debt of countries sponsoring election interference or on economic sectors vital to those countries’ economies.

If Trump didn’t have a history of playing down Russian election interference and sidling up to Putin, his new order might be enough to deter future attacks. But no one watching this administration can be confident that he would respond with more than minor sanctions. Congress should step in to send a clear message: Any nation seeking to interfere in U.S. elections will pay a price.