This February, Obama asked for just that authorization. Yes, the request came after the U.S. had already been bombing ISIS for six months. Yes, the White House claimed it already enjoyed the legal right to wage war under the congressional resolution passed after 9/11, and thus didn’t need the new authorization it was requesting. Still, the White House asked.

The Obama administration asked Congress to support a war resolution that expired after three years and prohibited “enduring offensive ground combat operations.” Many doves still found it too broad. Rand Paul offered an amendment—which some Senate Democrats backed—making clear the resolution authorized the president to fight ISIS only in Syria and Iraq. Hawks, by contrast, considered the resolution too narrow. Marco Rubio said it should read: “‘We authorize the president to defeat and destroy ISIL.’ Period.”

Therein lay the problem. In April, House Republican leaders announced that given opposition from both hawks and doves, the President’s proposed resolution could not pass, and thus, Congress would not vote. That’s where things have stood ever since.

Hawks like Rubio say that’s not a problem because, like the White House, they think the resolution passed three days after 9/11 provides authorization enough. As a result, they argue that Obama’s new resolution would actually constrain the war against ISIS, not only during his presidency, but during his successor’s. But constitutionally, the hawks’ argument is deeply unconvincing. The September 14, 2001 resolution said the President is “authorized to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001.”

ISIS cannot be such an organization since it did not exist on September 11, 2001. If you read the September 14, 2001 resolution as granting the President authority to attack ISIS, you’re conceding that any president can wage war anywhere as long as he says he’s fighting terrorism. Boehner, Cruz, and Paul rightly rejected that logic last fall, and they should still reject it today.

But you don’t hear Republicans saying that much anymore. 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.”

Voting on a specific war resolution—or resolutions—would make that evasion harder because it would force Republicans to define the parameters of the war they want to fight. And, just as importantly, it would force Hillary Clinton to do the same.

Two of the things GOP presidential candidates love talking about most are national security and the Constitution. Pushing for a vote on war with ISIS would be an excellent way to prove they’re serious about both.

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