Right now, the smart money, according to both Republican and Democratic aides, is on finding a trigger -- or more accurately a penalty -- to build into Harry Reid's plan to assure it leads to more deficit reduction in the future.
As currently devised, Reid's creates an ad hoc Congressional Committee tasked with authoring legislation to reduce the deficit by trillions of dollars -- likely through a combination of entitlement and tax reforms. It also raises the debt limit by over $2 trillion. Republicans won't accept the latter unless there's some assurance that the committee reports a bill, and Congress passes the bill. More accurately, they won't accept it unless future entitlement cuts are guaranteed to happen.
Hence the penalty. Under this scenario, the Reid plan would be amended to say that if by a certain date, an entitlement and tax reform package was not signed into law, something will happen. What that something is is still unclear, but members have batted around about a half dozen ideas, including enacting the Gang of Six plan, or President Obama's fiscal commission plan, or across the board spending cuts, or the rolling back of the health care law. The list goes on. The point is to prompt new spending cut legislation.
In either case, President Obama would not be allowed to raise the debt limit until one of those two things -- the enactment of an entitlement and tax reform bill, or the penalty -- actually happens.
They don't have long to figure out which way to go.