In a closed door caucus meeting today, a source who was present tells me, Speaker John Boehner reassured Republicans nervous about the ongoing budget standoff with Dems by vowing to “kick their ass.”

“If we stick together and keep the pressure on the Democrats, we’re going to win this fight,” Boehner told assembled Republicans, according to the source. “We’re gonna kick their ass.”

This is interesting not just for the colorful language, but because it sheds light on exactly what’s going on behind the scenes among Republicans as the budget standoff unfolds. I’ve got more for you on that.

As I noted below, Politico reported that Boehner has discussed a compromise with the White House centered on an additional $30 billion or so in cuts — far less than the $60 billion House conservatives want — with Cantor reportedly cut out of the loop of talks. Another source familiar with ongoing discussions confirms that this is true — but adds that there’s a crucial nuance that’s going unreported.

Here’s what’s happening, according to the source: The essence of Cantor’s disagreement with Boehner is that Republicans should not be starting with that number in talks with the White House, and that they should be starting with a higher level of cuts, because starting at $30 billion ensures that they will ultimately get less — which will be unacceptable to conservatives. Cantor does disagree with Boehner over how deep the cuts should ultimately be, but a more important point of disagreement is over how to handle these negotiations.

Cantor also seems to be trying to reassure House conservatives that he’s got their back in ongoing talks. Brian Beutler’s reporting indicates the same.

Here’s where Boehner’s “kick ass” quote comes in. Republican aides believe that Boehner is closing in on a $30 billion deal with the White House. They think he’s using rousing language before the caucus to signal to conservatives that he’s drawing a hard line in talks, partly because he knows that ultimately those talks will likely yield a deal that will be difficult to sell to them. Signaling a real fight now could make that sell easier later.

All of which is another sign of how difficult a balancing act the House GOP leadership is walking as the brinksmanship with Democrats intensifies and the shutdown deadline draws closer.