WASHINGTON (AP) — Democratic presidential candidates have spent the past year in a largely polite debate over domestic issues such as whether private health insurance should be eliminated in favor of a government-run program. That could change following escalating tensions this week between the U.S. and Iran.

The potential of open conflict involving the two countries was a reminder for many Democrats that for all the energy some progressive policy proposals have generated, the biggest decision a president makes often centers on whether and how to wage war. That could prompt some voters to reconsider which candidate they’ll back with just weeks to go before the Iowa caucuses formally usher in the primary season.

“In the short run, there’s no question” that the developments could reshape the race, billionaire environmentalist and presidential candidate Tom Steyer said in a phone interview. “If there are simmering tensions but no war, then I think Americans will go back to spending their time thinking about the economy and basic domestic issues.”

Last week, President Donald Trump ordered the killing of Gen. Qassem Soleimani, the head of Iran’s elite Quds Force. Iran retaliated by firing more than a dozen missiles from its territory at U.S. installations in Iraq. By Wednesday, both countries seemed to look for ways to de-escalate the situation. Speaking from the White House, Trump said he would impose new sanctions on Iran but didn’t announce additional military actions.

Now Democratic campaigns are assessing the political implications of a volatile week.

Former Vice President Joe Biden, once the top Democrat on the Senate Foreign Relations Committee and a leading Obama administration voice on international affairs, has sought to seize the issue to portray himself as the best candidate to take on Trump. Biden delivered extended remarks on foreign policy on Tuesday and has blasted Trump’s handling of it during campaign events.

“People are looking for the person who can help navigate us out of the mess that President Trump has created,” said Tony Blinken, Biden’s top foreign policy adviser.

But Vermont Sen. Bernie Sanders has also sought to appeal to Democratic voters by reminding them that he opposed the Iraq War in 2003 when few others in Congress, including Biden, dared to do so. And Trump bashed the Obama administration on Wednesday for failing to contain the Iranian threat, an argument he’d surely revive if Biden becomes the Democratic nominee.

Then there’s former South Bend, Indiana, Mayor Pete Buttigieg, who served in Afghanistan and is a combat veteran. The 37-year-old must overcome skepticism that someone his age could lead the country in a military conflict.

Massachusetts Sen. Elizabeth Warren, meanwhile, spent months rising in the polls by promising to dramatically remake the political and economic system and deliver universal health and child care and wipe out student debt. Her support appeared to be leveling off in recent weeks, though, and a greater focus on national security — an issue that hasn’t been at the forefront of her campaign — could make it tougher to recover.

All four have remained bunched near the top of many polls in Iowa and nationally, with no clear front-runner yet emerging. That’s why the next several weeks will be critical, especially if national security issues remain in the headlines.

Steven Brant, a 64-year-old who attended a Warren rally in New York on Tuesday night, called the tension with Iran a distraction “by an administration that wants us to forget there’s an impeachment process going on.”

In Des Moines, Iowa, Matthea Little Smith said that she’s backing Minnesota Sen. Amy Klobuchar and that developments overseas won’t change her choice because she thinks virtually any Democrat would be better than Trump.

“We have some brilliant folks that are running, and there’s not really a bad choice,” the 69-year-old said.

History shows foreign policy developments have altered past Democratic primaries in the final stretch before voting begins — with diverging results.

During the 2004 primary, former Vermont Gov. Howard Dean was thought to be surging and Massachusetts Sen. John Kerry floundering until U.S. forces’ capture of Saddam Hussein in December 2003 helped redraw the contours of the race barely a month before the Iowa caucuses. Kerry subsequently blistered Dean and other opponents with less foreign policy experience, saying there “are those in my own party who threaten to take us down a road of confusion and retreat.”