In a column this weekend, Ross Douthat posits that the GOP is most likely to find its way to a positive governing agenda if the contest to be its 2016 presidential nominee its Senator Rand Paul against Senator Marco Rubio. So who would he support?

His column treats the question as a tricky one. Douthat gives Rubio the edge on domestic policy, positing that he would "overhaul the tax code and safety net to support work, family and upward mobility."

On foreign policy, he prefers Paul, despite disagreements with his father. "The realism and restraint he’s championing seem wiser than the G.O.P.’s frequent interventionist tilt," he writes. "To imagine Rubio as a successful foreign policy president, I have to imagine an administration in the mold of Ronald Reagan’s, where hawkish rhetoric coexists with deep caution about committing U.S. ground troops—and I think there’s reason to worry we’d get incaution and quagmire instead."

Douthat ends without declaring a winner, implying a kind of equivalence: One guy wins domestic policy, the other wins foreign policy, so all told, they're sort of tied. But in this case, foreign policy should clearly carry more weight.

"Paul casts himself as the heir to the realist tradition in Republican foreign policy, while Rubio’s record and statements are more in line with the neoconservatism of the Bush era," Douthat writes. "To use specific Obama-era examples, a Paul-led G.O.P. would presumably oppose Libya-style humanitarian interventions and eschew gambits like our effort to aid Syria’s rebels, while a Rubio-led G.O.P. might be willing to put American boots on the ground in both situations. These are not small differences, and they might be magnified in larger crises."

That's putting it mildly.

It's easy to imagine a "larger crisis," because just such a crisis happened already. Rubio would fill his White House with people who still regard the Iraq War as a good idea. Paul would tap people who believe it to have been an ill-conceived mistake. Rubio would ally with people who sing, "Bomb bomb bomb, bomb bomb Iran." Paul represents the opposing foreign-policy faction in the GOP.

To present the difference between them in terms of the War in Libya is to minimize its importance. Imprudent as it was, Libya didn't cost much in blood or treasure, whereas Iraq is clarifying. Douthat may believe that a Rubio domestic agenda would serve America better than a Paul domestic agenda. But is the difference so great as to outweigh the risk of a Rubio war that kills 4,489 Americans, wounds tens of thousands, exposes hundreds to chemical agents, and triggers a PTSD epidemic? Is Rubio's tax plan so good that its worth risking another $6 trillion war tab?

It's too risky to put another Iraq hawk in the White House, especially when they've given no indication of having learned anything from that historic debacle. Every president makes mistakes. Every president favors some dumb policies. Rubio seems more likely than his rival to favor the sort of mistake that ends in a tear-stained wall where the names of dead 19-year-olds are engraved in polished stone.