SAUL LOEB / AFP / Getty Images Speaker of the House John Boehner and Democratic leader Nancy Pelosi in Washington on May 15, 2013

Nearly 1,500 are dead in the worst chemical attack in the 21st Century, including hundreds of children. A red line has been crossed and America’s prestige and credibility at stake, not just in Syria but for any rogue nation looking to challenge the United States: Iran, North Korea, Venezuela. But getting Congress to approve even limited action in Syria, as President Obama asked them to do today, is going to be tough.

Here are three reasons why:

Weak House: The House tried and failed several times to get war authorization through on Libya. They gave up trying when U.S. military action there ended. And Libya had the backing of the United Nations, NATO and the UK. Getting something through the House on Syria will be even harder than passing approval on Libya. With Libya, there was only moderate public interest in the Congressional machinations, since the authorization was retroactive given that President Obama had already approved U.S. involvement. This time around, all eyes will be on the House and the pressure will be intense. There’s a reason House Speaker John Boehner didn’t call on Obama to seek a vote of approval for action in Syria: This was one nightmare he was keen to avoid.

Splits both parties: Remember the 2004 election when President George W. Bush went around scaring folks about how Democrats were weak on defense? The days where Iraq and Afghanistan were partisan issues have gone. Washington has reverted to a foreign policy more akin to President Clinton’s days where both parties split on intervention. Now, as it was in the 1990’s, you have Democratic doves aligning with isolationist Libertarians. They face off against Republican Hawks and Democratic bleeding hearts. This makes whipping votes complicated, to say the least. It also makes Syria less of a partisan issue, which is the way going to war used to be. By throwing this to Congress, Obama is basically challenging all the backbenchers who have been vociferous in their criticism in the last 10 days—Liberals fearing another Iraq, Hawks saying we need to go farther on regime change—to stand up, be heard and unite behind a military action. It will likely be chaotic. Already two Republican Senate hawks, John McCain of Arizona and Lindsay Graham of South Carolina, have announced they will not vote to authorize force in Syria unless Obama commits to an “an overall strategy that can change the momentum on the battlefield, achieve the President’s stated goal of Assad’s removal from power, and bring an end to this conflict.” The White House has previously argued that there is no acceptable military solution for the civil war in Syria.

Unpopular: Polls show most Americans don’t want to see any kind of intervention in Syria, so if Congress votes to support this, they will be going against their constituents’ wishes, which is never easy especially for those up for reelection. Members are going to have to defend the intelligence and make the case to their supporters why it’s important to do this. To that end, a limited engagement is better, as they can make the argument that this isn’t the beginning of another decade of war.

Obama has a tough lift in the coming weeks convincing Congress—and the American people—to support his decision. He’ll have some allies to help him: Surely the American Israel Public Affairs Committee will help whip a vote, since having a failed state on the Israeli border isn’t appealing and the next looming red line is Iran. But that doesn’t make victory a sure bet. Obama won his office, after all, arguing for withdrawal from the Middle East. Now he has set up a situation where his presidency—and the reputation of Congress—could be harmed if Congress does not approve more intervention.