Republicans are gaining significant ground in the fight over federal spending, but a dispute has been simmering within the GOP's ranks over just how aggressively to confront the White House and the Democratic Senate.

As one might expect, the tea partiers are clamoring for confrontation, while Speaker John Boehner and GOP leaders continue pressing ahead toward the campaign goal to cut $100 billion.

House Republicans have passed two stopgap measures that achieve that level of cutting on a temporary basis. In lieu of bipartisan agreement on a longer-term spending plan, a two-week stopgap funding bill passed March 1 cut $4 billion from last year's spending levels. A three-week extension, passed on Tuesday, cut $6 billion. Multiply those cuts out over an entire year, and House Republicans hit their $100 billion mark.

But conservatives in the party have grown impatient, and if the pressure on GOP leaders isn't intensifying, it's at least been sustained. Unity is turning into dissent.

Republicans were almost completely united in passing $60 billion in cuts on Feb. 19 (only three voted against it), though the plan was destined to be rejected by Senate Democrats. On March 1, only six Republicans broke ranks to vote against the first temporary measure. But on Tuesday, 54 sided against leadership and opposed the current three-week extension. By the numbers, Boehner and Republican leaders actually needed Democratic votes to pass it.

The "no" coalition was made up of conservatives and tea partiers. Reps. Michele Bachmann (Minn.), Allen West (Fla.), Raul Labrador (Idaho), and Mike Pence (Ind.) were among them.

Going forward, they don't want to continue with piecemeal victories. They want to aggressively confront the White House and the Democratic Senate, getting the big picture settled and putting a government shutdown on the table.

Now is the time for Republicans to "pick a fight" over spending cuts, Pence told National Journal's Major Garrett this week.

Tea party activists are keeping up the pressure on GOP leaders. Judson Phillips, the Tea Party Nation founder known for controversial screeds, criticized Boehner on the group's website:

Irony isn't quite the word here.  On Tuesday, while John Boehner, the House leadership and the Party of Corruption were off cheering about cutting $6 billion from the budget, the national debt rose by $72 billion.

What do we call something like that?  Certainly not "winning!" ...

Boehner, meanwhile, has been touting the cuts, letting people know that the $100 billion pledge is being kept. A press release sent Friday read:

Republicans pledged to listen to the American people and make the spending cuts economists say we need to end the uncertainty facing job creators so they can start hiring again - and they're keeping that pledge. The Democrats who run Washington, meanwhile, are divided and "haven't outlined what specific cuts they'd prefer" nor "put forward a long-term spending plan."

Boehner has firmly stated that he does not want a government shutdown. It's a political battle that can be lost, depending on who gets blamed, and, more significantly, Boehner has made a moral case against it.

"We have a moral responsibility to address the problems we face.  That means working together to cut spending and rein in government-not shutting it down," Boehner said in a February speech, even as he placed blame for the spending stalemate on Democrats for not accepting more of the GOP's proposed cuts.

As has been the case before, and as many assumed would be the case in a GOP-majority House, Boehner is caught between a restless conservative contingent and his own, more staid perceptions of how a political fight like this should work.

And if the government shuts down, it will do so because of a split within the GOP's ranks.

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