Though the Obama Administration is insistent that Congressional authorization is not required to take action of limited scope in Syria, Obama is seeking approval from Congress anyway. There have been several explanations as to why that is. For starters, it's good politics. Nearly 80% of Americans surveyed want him to get Congressional authorization before taking any action, regardless of whether they support intervention or not.
There's also the looming debt ceiling deal coming up in the weeks ahead. And while its fate is uncertain in the House, immigration reform is still a thing. Had Obama snubbed Congress and went ahead with strikes on Syrian targets unilaterally, that could have sparked additional tension between the White House and Congress during a time where they need congressional points to keep the government running. Not getting anything from the House on immigration reform after it passed the Senate with a filibuster-proof majority would be disappointing, but rejecting raising the debt ceiling would be catastrophic.
It's also worth noting that five years ago, candidate Obama probably would have wanted the president to seek authorization from Congress before striking Syria in this situation. And the international support and coalition we enjoyed in our intervention in Libya over two years ago is notably absent when it comes to Syria. That likely changed the commander-in-chief's calculus when it came to deciding whether or not to go to Congress for approval.
There have also been theories that Obama does not actually want to get involved in Syria; he just wants to look tough, knowing full well a request for authorization would die in Congress. This is under the assumption that whatever political capital he spends on getting a request for military action rejected by Congress pales in comparison to the toll of actually getting involved in Syria. On the flip side, the other more likely theory is Obama believes this can get through Congress and intervening in Syria is the right thing to do.
Whatever the reasons, Obama is going to Congress for approval on military intervention in Syria. But what happens if Congress rejects that request?
The first long-term political repercussion this would have is Obama and future presidents would be very reluctant to go to Congress again for military intervention whenever there is a case to be made that they don't have to. Congress would essentially throw away whatever leverage they'd have by giving up their seat at the table in future limited-scope interventions. This could cause a constitutional crisis over the role Congress plays in authorizing military action and how broad the president's powers are, and we could likely see a case at the Supreme Court down the road that ends up further defining or even limiting executive power.
What happens if Congress rejects Obama's proposal and he still goes through with military strikes in Syria?
Obama has made it very clear that he does not believe he needs Congressional authorization, but is seeking it anyway out of courtesy because he is confident he'll get approval from Congress. The administration has also been reluctant to answer whether or not Obama will still order strikes to be launched in the event of Congressional rejection. In fact, whenever they're asked about it, the Obama administration is often reluctant to even entertain the idea that Congressional rejection is even in the realm of possibility.
But what if, in worse-case-scenario, Congress rejects authorization for intervention and the situation in Syria escalates to a point where Obama feels he must intervene, without the blessings of Congress if he must?
In that instance the case must be made that there was a direct and imminent threat to U.S. national security interests and a humanitarian argument would hold little weight. Even still, there would be calls from some Republicans in Congress for impeachment, a call that would ultimately go unanswered as Boehner is in agreement with Obama on Syria and knows all too well the potential political backlash his party could see if they went through with it.
Even Senator John McCain, one of Obama's biggest allies in Congress on Syria, went so far as to say that Obama could be impeached if he put troops on the ground in Syria. But that was more so to reassure members of Congress who are on the fence over Syria that ground troops are not at all an option and this exercise will be limited in scope.
The best course of action Congress can take without tarnishing its credibility and to actually strengthen its influence in future military operations is to authorize Obama's request for strikes in Syria, but limit the scope of it with language in the bill they end up passing.