Donald Trump has spent months defending the war with Iran.

Now a new CNN poll suggests he's increasingly having trouble convincing members of his own party.

A CNN poll conducted by SSRS finds Republican approval of Trump's handling of the Iran conflict has fallen 13 percentage points since March, dropping from 73 percent to 60 percent.

That's still a majority.

But the direction is unmistakable.

And outside the Republican base, the numbers are considerably worse.

Across the country, just 26 percent of Americans approve of Trump's handling of the Iran war, down from 33 percent in March.

Nearly two-thirds — 64 percent — say the United States is not winning the war.

Another 70 percent say Trump's decisions involving military action against Iran have hurt the United States, while roughly three-quarters say the president does not have a clear plan for dealing with the conflict.

For a president who returned to office promising strength abroad and repeatedly emphasizing his ability to resolve international conflicts, those numbers represent a significant deterioration in public confidence.

But perhaps the most politically significant warning is coming from inside Trump's own coalition.

Among Republicans and Republican-leaning independents under 45, 53 percent disapprove of his handling of the war.

Among Republicans and Republican-leaning independents who do not identify with the MAGA movement, 54 percent disapprove.

Those aren't Democrats.

They're voters from the political coalition Trump has depended upon.

Republicans Are Still With Trump — But Less Than Before

It would be inaccurate to say Republicans as a whole have abandoned Trump over Iran.

Most haven't.

Sixty percent still approve of his handling of the conflict, and 70 percent of Republicans surveyed believe the United States is winning the war.

But compared with March, Republican support has clearly weakened.

CNN Washington bureau chief David Chalian described the polling as a “political disaster” for Trump, pointing specifically to the 13-point decline in Republican approval.

That is Chalian's assessment, not a conclusion of the poll itself.

The numbers, however, show a clear shift.

And Iran isn't Trump's only foreign-policy problem.

Just 29 percent of Americans approve of his handling of foreign affairs overall, the lowest rating CNN has recorded for Trump across his two presidential terms.

Americans Question the Cost

The public's skepticism extends beyond whether America is winning.

According to the poll, 76 percent of Americans say the war has not been worth the loss of American lives and government spending.

Seventy percent believe Trump's military decisions involving Iran have hurt U.S. interests.

And 78 percent say Trump isn't doing enough to bring the conflict to an end.

Those attitudes are occurring while Americans are also dealing with the economic consequences associated with turmoil in the Middle East, including sharply higher fuel prices.

For voters filling their tanks, paying household bills and watching another American military conflict continue without a clear endpoint, foreign policy is no longer something happening thousands of miles away.

It's increasingly something they can see in their wallets.

The Coalition Is Showing Cracks

Trump's political strength has long depended on extraordinarily durable support among Republican voters.

That's what makes these numbers notable.

The CNN poll does not show Republicans broadly abandoning Trump.

It does show that support for his handling of Iran is significantly lower than it was six months ago — with particularly pronounced dissatisfaction among younger Republicans and Republicans outside the MAGA movement.

That distinction matters.

Trump still commands majority Republican support on Iran.

But the coalition isn't as united as it was.

And after months of war, rising fuel costs and repeated questions about how the conflict ends, the administration is now facing a problem that can't simply be dismissed as Democratic opposition.

Some of the people questioning Trump's Iran policy are coming from inside his own political camp.

The question now is whether that erosion stops here — or continues as the war drags on.