It’s all going to come down to the trigger.

Look closely at the Reid and Boehner bills. The first round of cuts are pretty much the same. The joint congressional committee charged with recommending further deficit reduction is pretty much the same. The difference is that Boehner’s bill forces them to act. He ties a future increase in the debt-ceiling to the successful passage of their proposal. Reid’s bill has no such trigger. And many of the participants in this process say that is the space where a deal will be made -- or not made.

Democrats dismiss Boehner’s current offer completely. At the New Republic, Jonathan Chait piquantly compared it to “a kidnapper who offers to give you back your child in return for $100,000 and your other child.” A senior Democratic aide in the Senate is even blunter. “That’s the one line in the sand we’ve drawn this whole time. We can’t be revisiting this in another six months.”

Most think the likely compromise is a trigger that would impose automatic, across-the-board cuts in spending if the committee fails in its mission. But Senate Democratic leadership isn’t so sure. They worry that a spending-cuts only trigger is heads, Republicans win; tails, Democrats lose. “The idea of triggers with just cuts is a non-starter. Republicans would just deadlock the committee and get the cuts they want,” continues the aide. “If there is a trigger it would have to be balanced.”

The White House proposed a balanced trigger in April: It would have automatically raised taxes and cut spending if America wasn’t on a path to balanced budgets by 2014. In his remarks on Friday morning, Obama reiterated that support. “if we need to put in place some kind of enforcement mechanism to hold us all accountable for making these reforms, I’ll support that too if it’s done in a smart and balanced way.”

But privately, they’re less concerned about a spending-only trigger, which was seriously considered during their negotiations with Boehner.They point out that Republicans might want to cut spending, but they don’t want the blame for automatic, untargeted spending cuts that slash away at Social Security, Medicare and defense during an election year. But that’s cold comfort to some Hill Democrats who listened to Boehner’s Tuesday interview with Rush Limbaugh.

”I don’t believe that the Republicans on this committee that get appointed are going to vote to increase taxes,” Boehner said, “and if they did, I don’t believe the House of Representatives would approve the report of the joint committee.” And they reasonably wonder why they should believe that a party that is willing to risk default would blanch at the prospect of spending cuts.

Jim Horney, a budget expert at the Center on Budget and Policy Priorities, thinks that a spending-only trigger misses the point of these devices. Horney, who worked on the budget deals in the 1980s and 1990s, argues that the point of these mechanisms is “to force both sides to negotiate sensibly.”

Take the Gramm-Rudman-Hollings Balanced Budget Act, he says. “They figured that Democrats cared about spending programs. So half the cuts would come from domestic programs. and they realized that what Ronald Reagan cared about wasn’t taxes so much as defense. So half the cuts came from defense. But what gets the attention of Republicans today is not defense. It’s taxes. So if you’re going to use the basic idea sequestration had in its original incarnation, it has to include revenues to bring them to the table.”

But that assumes the trigger is there to force both sides to negotiate in good faith. If it’s just there to get Republicans to agree to a debt-ceiling increase that takes us through to 2013, it’s obviously a different story.