This article originally appeared on Slate.

Republican presidential candidates are having trouble answering hypothetical questions about what they would have done in Iraq. First Jeb Bush stumbled last week when asked, knowing what we know now, if he would have launched the same war his brother did. Then on Sunday, Sen. Marco Rubio spent the morning going around the mulberry bush with Fox's Chris Wallace. Wallace wanted Rubio to explain how he could say the Iraq war wasn't a mistake because Saddam Hussein was removed from power while also saying that knowing what he knows now he wouldn't authorize such a war. Rubio's position: It was not a mistake--and he will never repeat it.

Here's the problem for Rubio. When you are asked if the war was a mistake and you cite the removal of Hussein, you appear to be making a judgment about the entire war and its costs. You are echoing Dick Cheney. Yes, the amount and kind of weapons of mass destruction that served as the rationale for war turned out not to exist, but deposing the Iraqi dictator made it worth the effort. If that's Rubio's view of regime change that tells us something about how he thinks about the world and America's place in it. It also warrants asking the underlying hypothetical question (and probably a number of follow-up questions, too).

Rubio told Wallace the war was not a mistake because Bush made the best call at the time based on the available evidence. His first answer rendered a final verdict on the war; it was worth it to remove Hussein. The second one asks us to travel back to 2003 and render a verdict before the bombs started falling. These are two different answers the candidate is trying to treat as the same.

Get Breaking News Delivered to Your Inbox

The narrow lane that Rubio is trying to manage here is that he doesn't want to say that the war was a mistake. That's politically toxic because it puts a firmly negative judgment on a foreign policy worldview Rubio largely shares. More important, it suggests that the men and women who died in that war died in vain. This is the same lane Hillary Clinton tried to navigate during the 2008 campaign when she backed away from her vote authorizing the war, but refused to call that vote a mistake. She said she didn't want to use that word while combat operations were still taking place. Many Democrats believe this equivocation cost her the nomination that year.

To avoid danger, Rubio and others argue that the reason the war was not a mistake is that George Bush made the right call based on the information he had at the time. This position puts them on more defensible political ground. Seventy percent of the country may think the Iraq war wasn't worth it now, but a lot of them thought the war was worth it in the spring of 2003, when more than 70 percent of the country supported the war.

But even if you thought you were right in the first place, if your decision turns out to be wrong, then that is commonly called a mistake. That's ultimately what Clinton concluded when she finally admitted in her book Hard Choices that her vote was a mistake. "I thought I had acted in good faith and made the best decision I could with the information I had. And I wasn't alone in getting it wrong," Clinton wrote. "But I still got it wrong. Plain and simple."

This is what was always so powerful about Ronald Reagan's distinction about liberals: Their hearts were in the right place, but that didn't make them right when their choices led to bad outcomes. "It's not that our liberal friends are ignorant," he said in his famous 1964 "Time for Choosing" speech. "[I]t is that they know so much that isn't so."

That is also the foundation of Republican critiques of the Obama administration on everything from misreading the Arab Spring to underestimating the growth of ISIS. The president may have thought he knew what he was doing but he was wrong. Former CIA deputy director and CBS senior security contributor Michael Morrell says as much in his new book about the Arab Spring:

We thought and told policy-makers that this outburst of popular revolt would damage al-Qaeda by undermining the group's narrative ... [but] ... the Arab Spring was a boon to Islamic extremists across both the Middle East and North Africa. From a counterterrorism perspective, the Arab Spring had turned to winter.

Of course, there are Republicans who think that Obama is so confused about the world that these are mistakes of a different order. They are policies designed to fail because he fundamentally misunderstands the world. That may be so, but that's a debate about the root cause of the mistake, not whether the mistake should be called something else.