The reason is that trying to craft a war resolution that could win majority support would require them to make difficult choices. Right now, GOP presidential candidates can demand that Obama destroy ISIS while remaining vague on how exactly to make that happen. A vote on specific language would force senators like Cruz, Rubio, Paul, and Lindsey Graham—along with the other Republicans running for president—to answer hard questions. Do they support long-term U.S. ground operations? Should the war be open-ended? Should it be limited to Iraq and Syria or cover the entire globe?

But that’s precisely the kind of debate the Constitution requires. And it’s a debate America needs. Ever since last summer, when ISIS grabbed headlines with its military offensives and ghastly beheadings, Obama’s hawkish critics have largely tried to have it both ways. They’ve depicted ISIS as a massive threat to the United States. And yet recognizing the public’s desire to avoid another land war, they’ve mostly avoided proposing the large-scale deployment of U.S. troops. As the New York Times recently put it, “most of the Republicans [running for president] are also reluctant and even evasive when it comes to laying out detailed plans [for fighting ISIS], preferring instead to criticize Mr. Obama’s war strategy.”