When Sen. Ron Johnson was asked last week why GOP lawmakers were so reluctant to assert their legal authority on matters of national security, the Wisconsin Republican replied that it’s a mistake to look to Congress for limits on presidential power. “I think the primary restraint on any president of [the] United States is public opinion,” the senator told NPR.

That wasn’t much of an answer, in part because of how our constitutional system is supposed to work, and in part because Donald Trump can’t run for president again and doesn’t seem to care much whether the American public supports his priorities or not.

But for Republicans who will have to face voters again, public attitudes remain quite relevant, and as the war in Iran extends into its second week, there’s fresh evidence that a majority of Americans are not on board with the latest military offensive in the Middle East. The latest national Quinnipiac University poll found:

Fifty-three percent of voters oppose the U.S. military action against Iran, while 40 percent support it. … Seventy-four percent of voters oppose sending U.S. ground troops into Iran, while 20 percent support it.

‘Voters are unenthusiastic about the air attack on Iran and there is overwhelming opposition to putting American troops on Iranian soil to fight a ground war,’ said Quinnipiac University Polling Analyst Tim Malloy.

The same survey data also found that 55% of Americans agreed that Iran did not pose an imminent threat to the United States, the White House’s dubious claims notwithstanding; 59% said the president should have gone to Congress to approve the mission; and 62% concluded that the administration had not provided a clear explanation of the reasons behind military action against Iran.

The president’s overall approval rating in the Quinnipiac poll, meanwhile, was 37%.

The results dovetail with the latest NPR/PBS News/Marist poll, which was released late last week and similarly found 56% of Americans oppose the war. Other polls from last week, including surveys from Reuters/Ipsos, NBC News, CNN and The Washington Post all pointed in similar directions.

All of the data showed a predictable partisan gap — Republican voters have been more likely than Democrats and independents to side with the administration — but by any fair measure, the war does not enjoy broad public support.

Indeed, the military offensive is unpopular at a historic scale: The New York Times did a comparison analysis and found that support for the strikes in Iran “is far lower than what it has been at the beginnings of previous foreign conflicts.”

Over the last several decades, there’s been a relatively consistent trend in public opinion: Conflicts enjoy broad support at the outset, but public attitudes turn negative as wars drag on.

The current war, however, is unique: It’s already unpopular.

I don’t doubt that the data is discouraging for the White House, but I also continue to believe that Trump has no one to blame but himself for the American mainstream’s skepticism.

Ahead of the U.S. offensive in Iraq in 2003, George W. Bush at least made the effort to prepare the nation for war. The president’s policy proved disastrous, but before launching the offensive, he told the public what he was doing, why he was doing it, why he saw the mission as necessary and what he hoped to accomplish. While the failed policy ultimately proved wildly unpopular, polls showed strong public support when “shock and awe” got underway in Baghdad.

Trump didn’t bother with any comparable efforts and never made the case for war. The resulting polling data was inevitable.

This post updates our related earlier coverage.