President Donald Trump has strong Republican backing for his war with Iran. It might fade with time.

Congressional Republicans clearly have no desire for a drawn-out conflict in Iran, even as they assert that Trump can avoid his predecessors’ entanglements in Iraq and Afghanistan. Those wars cost thousands of American lives, drained political support from multiple presidents, and demonstrated the perils of nation-building.

To avoid a similar outcome, the administration already has a congressional clock to keep in mind. Under current law, Trump has 60 days before Congress would have to authorize the war with Iran, with an additional 30-day withdrawal period under the War Powers Act.

“As supporters of what the president’s doing, in 60 to 90 days, we start losing our high ground legally,” Sen. Kevin Cramer, R-N.D., told Semafor. He praised the Trump administration’s handling of the war and compliance with Congress so far but warned that “I don’t know any scenario where a war gets better with the public … war fatigue is real, and it happens quickly.”

Trump’s advisers are likely to clear their first hurdle Wednesday, when the Senate votes on his war powers, but their Hill briefings this week will determine the number of GOP defections. And their bigger challenge is to shape the initially rocky public perception of an open-ended war Trump chose — one that his opponents are already likening to George W. Bush’s invasion of Iraq.

“We’re not the Bushes,” one White House official told Semafor. As to the 60-day congressional timeline, the official said: “I wouldn’t want to hamstring us by saying anything beyond what we’ve already said: Four to five weeks is when we hope this will conclude … everyone’s optimistic about that.”

Sen. Jerry Moran, R-Kan., sided with the Trump administration on previous war powers votes this Congress but said the Iran conflict “seems different … more serious, more lengthy.” He’s currently undecided.

“There is a high, significant potential outcome for good, but it’s a high-risk effort,” Moran added. “I don’t think there’s anybody who could say it’s going to be over by a certain date.”

Vice President JD Vance, who endorsed Trump for 2024 with the argument that he’s “started no wars,” has lately echoed the commander-in-chief’s assessment that the US has “the capability to go far longer than” four or five weeks. Administration officials also insist that Trump will not bring the US into an extended conflict. Past presidents have also sought to skirt the War Powers Act.

The administration is preparing options for a new Iranian government if it integrates into the Middle East and drops its nuclear weapon program, according to one senior Trump administration official — a sign of a potential quick end to the war.

“We are working on what a sanctions relief package could be in the future, if there is a framework that’s agreed to with a new government,” the official said.

Vance — historically a staunch anti-interventionalist — argues that this war differs from past lengthy global conflicts because Trump “has clearly defined what he wants to accomplish.”

But there’s quiet acknowledgement that no one truly knows how long operations against Iran will last, or what the end result will be.

“We don’t” know that this won’t be another Afghanistan, one person close to the White House argued, before adding: “I don’t see how you can put a timeline on it.”