The Senate's "Five Guys," a.k.a. the "Gang of Six" minus Sen. Tom Coburn who suddenly jacked up his demands and then bolted, is trying hard to stay relevant to the budget debate. The trouble is that the other Republicans won't go public with their deal unless Coburn joins, and Coburn has little incentive to do that:

He emphasized that the perfect cannot be the enemy of the good and stressed to reporters that many of Coburn’s ideas remain in the package after the latest group meeting on Tuesday.
Standing next to Warner, Chambliss said, “It is important that at the end of the day … we have a strong bipartisan group, and I hope that Tom Coburn is a member of that when we conclude and make our presentation.”

This, if you recall, is exactly what happened during the Senate health care negotiations. It was even called the Gang of Six. Conservatives started pressuring the Republican members, and first the most conservative one peeled off (with health care it was Mike Enzi) which in turn made the next-most-conservative Republican hesitant to keep negotiating, until the whole thing fell apart. The same dynamic is also at work in which the Republicans can negotiate for certain terms, abandon the deal, and then have those conditions remain in the legislation anyway. It doesn't exactly give you a strong incentive to cooperate.