In recent years under President Vladimir Putin, Russia has annexed Crimea, made multiple military incursions into Ukraine, meddled in elections in the United States and elsewhere, allegedly poisoned a former spy and his daughter living in the United Kingdom, sponsored cyber attacks and espionage on computers worldwide, and kept Syrian President Bashar Assad in power even as he used chemical weapons to kill his own people on multiple occasions. Small wonder that a new poll finds more than two-thirds of Americans support tougher sanctions on Russia — as do senior national security advisers including, most notably, United Nations Ambassador Nikki Haley. So why doesn’t President Donald Trump?

His explanation for reversing the sanctions announced Sunday by Ms. Haley — which would have penalized Russian companies found to have assisted in Syria’s chemical weapons production — was, according to White House Press Secretary Sarah Huckabee Sanders, a desire to have a “good relationship” with Russian officials while still being “tough” on the country. Yet as necessary as the recent U.S. military airstrike against Syria may have been, it hardly affected Russia’s long-term interests in the region. It didn’t take Mr. Assad out of office or change the balance of power in Syria’s civil war. It merely made the point that the U.S. and its allies will not tolerate chemical weapons on the battlefield or against civilians, a message delivered not just to Mr. Assad but to a variety of dictators and regimes around the world.

Ms. Sanders has indicated that Mr. Trump may yet impose the sanctions, but what would that take? An even more deadly chemical attack than the April 4 assault that killed more than 70 people outside Damascus? And of all the places and times to go soft on Mr. Putin, why make it here and now? Isn’t it better to go after Mr. Assad’s enablers on an economic basis than lob ordnance into the country where it may injure or kill innocent people?

Making the reversal all the more ridiculous was top White House economic adviser Larry Kudlow’s attempt to shift blame to Ms. Haley suggesting she had suffered “momentary confusion” and gotten ahead of the president. Ms. Haley’s response, “I don’t get confused,” followed by an apology from Mr. Kudlow points to where the truth in the matter lies.

The Washington Post-ABC News poll conducted last week certainly found no shortage of Americans embracing sanctions against Russia. Not only do 68 percent of Americans support tougher sanctions, but they do so across party lines with 68 percent of Republicans and 68 percent of independents sharing that view. That’s consistent with congressional action on the subject. Last summer, Congress gave overwhelming bipartisan support to new sanctions — 98-2 in the Senate and 419-3 in the House. But it took until last month for the Trump administration to finally impose those sanctions (and it refrained from imposing the full slate of what Congress had approved).

Add to that the consistent praise President Trump has showered on Mr. Putin, most recently congratulating him for winning what was essentially a rigged election, and special counsel Robert S. Mueller III’s ongoing probe into Russian meddling and the possibility Trump associates encouraged or coordinated that interference (or that the president has actively tried to block the investigation), and it’s really no wonder that people like former FBI Director James Comey might openly speculate whether Russia had something on President Trump. That’s not Mr. Comey being catty or vengeful, it’s the obvious question given the president’s peculiar behavior.

Just this week, the U.S. and Britain warned Russia against cyber attacks aimed at both government and private targets, raising the possibility of tit-for-tat escalations that might drift into the physical world. But how effective is that message when the leader of the most powerful nation shows such a consistent willingness to back down from punishing Mr. Putin, whether it’s over election meddling or chemical weapons attacks? Why should the Russian leader think the U.S. is any more resolute about cyber security?

What makes this circumstance all the more incredible is how it is countenanced by the party of Ronald “Trust, but verify” Reagan and the “peace through strength” mantra. We don’t relish the prospect of another Cold War, but it’s not difficult to discern a pattern here of an increasingly emboldened Russia seeking to push the limits of a president so desperate to have a “productive relationship” with Mr. Putin that he’s willing to overlook a variety of transgressions that most Americans find alarming. Whether there was “collusion” prior to the election or not, there’s something highly suspect about Mr. Trump’s behavior toward Russia now.