The affordability question Republicans can't escape

One issue is breaking through even among the most loyal Republican supporters: gas prices .

Why it matters: Republicans promised to slash gas prices.

But the Iran war sent them soaring, up 37% since President Trump took office .

Republicans call it temporary.

But there are limits to what voters will accept.

On recent campaign trips with House Majority Whip Tom Emmer (R-Minn.) and Majority Leader Steve Scalise (R-La.), gas prices were the most frequent concern raised at events attended by Axios.

These weren't rooms full of undecided voters.

They were GOP donors, activists and supporters who had turned out to help Republicans win in November.

Zoom in: The first question Scalise fielded at a campaign event for Republican Marty O'Donnell in Nevada was about high gas prices.

"Everyone's always worried about gas prices," the attendee said, asking whether Republicans could do more to promote Trump's efforts to expand domestic energy production.

Another attendee pointed to the gas-price difference between California and Oregon on a recent trip, and asked whether Congress could intervene to ease state restrictions.

Scalise acknowledged the impact of the Iran war on gas prices — and said they'd fall once it's resolved — but blamed Democratic energy policies for making the U.S. more vulnerable to rising costs.

Zoom out: Emmer faced similar concerns during a recent campaign trip through North Carolina and Virginia.

"Four-dollar gas, five-dollar diesel, six-dollar diesel, totally unacceptable," Emmer told supporters at a North Carolina fundraiser.