Trump has been able to keep oil prices low. But that power may not last forever.

President Donald Trump on Saturday abruptly called off the “biggest attacks since World War II” against Iran in favor of negotiations, the latest in a seemingly endless series of whiplashes in the conflict. The energy markets, which typically favor stability and predictability, responded with little more than a shrug. Crude prices dipped slightly and gas prices remained steady. Even as the war stretches past the six-month mark and the midterms creep closer, Trump has been able to keep retail prices lower than experts say they should be through the sheer power of promises – which have yet to come through – of a swift end to the conflict. On Monday, he took that a step further, chastising the major oil companies for “making too much money” off global oil shortages as a result of the war. “They better cut the retail price, the consumer price,” Trump said. “I’ll say it loud and clear. I’m not happy about it.” But Trump’s ability to jawbone the markets may be diminishing at a critical time, three months before the midterm elections when control of Congress is hanging in the balance and his approval is sinking to new lows amid voter anger over cost of living concerns. It comes as global crude oil supplies are running low, the war threatens more energy flows, refiners are running out of spare capacity and the administration has few tools to keep gas prices low. “Labor Day is the point where gas prices are baked into the election,” said Republican pollster Frank Luntz. “That last summer trip determines how voters evaluate their cost of living.” And the higher gas prices come at a time when Trump repeatedly promises to escalate the war and then says it’s almost over a few hours or days later. That is starting to degrade his ability to cause price drops, a former adviser cautioned. “His credibility has been a little bit shot,” said a former Trump adviser close to the White House, granted anonymity to avoid reprisal. “The markets aren’t paying attention to him, they’re paying attention to what’s happening and, with respect to oil prices, it is a huge liability for the Republicans,” the adviser said. Trump on Monday acknowledged that dynamic but expressed no urgency. He told reporters in the Oval Office that he was in no rush to end the conflict, though he acknowledged the need to fully reopen the Strait of Hormuz, through which about 20 percent of global energy supplies flowed before the war. He hinted at the midterm stakes for his party if the conflict does not end soon. “I’m under no time constraint,” he said. “I don’t happen to be running, but a lot of very good Republicans are running.” Trump’s ability to move the markets may be the only tool the administration has left to keep gas prices in check, said Rory Johnston, an oil market researcher and founder of the Commodity Context newsletter. The Trump administration has drawn down the U.S. Petroleum Reserve to its lowest level since President Ronald Reagan’s first term. Oil majors are warning that the lack of refinery capacity could keep prices high for the foreseeable future. “The market is so entrenched on this idea that eventually this will resolve by Trump deciding and ceding some ground on some issue, likely kind of even symbolic control of the Strait of Hormuz,” he said. “So the market’s going to be constantly watching for any sign that he’s shifting there.” While experts continue to marvel at Trump’s ability to get the markets to bend to his whims, there is little consensus on when that power will dissipate. Trump has “less credibility” in terms of moving markets, but it has not totally dissipated, Patrick de Haan, head of petroleum analysis at pricing service GasBuddy. “I don’t think credibility completely goes to zero,” he said. “Hard to know though when it really bends.” Trump’s push to keep energy prices low has also been buoyed by reduced Chinese oil imports, the successful rerouting of about 7 million barrels per day of Saudi Arabian crude through the Red Sea and releases