For a few Republican lawmakers, perhaps the biggest battle facing House-Senate negotiators on a huge budget bill isn't a high-profile issue like cutting food stamps and Medicaid or opening a stretch of pristine Alaskan coast to oil drilling.

It's milk.

Specifically, it's the Milk Income Loss Contract program that pays dairy farmers when prices drop.

For some, like Rep. Mark Green of Wisconsin and Sen. Rick Santorum of Pennsylvania, their political lives could be at stake. Green and Santorum represent states dotted by family dairy farms. Their battle is with Republican colleagues from Western states with much larger dairy operations.

Compared with hot-button issues, the internal GOP battle over the Milk Income Loss Contract program seems pretty obscure. The program expired Sept. 30. Extending it for two more years would cost taxpayers $1 billion.

Green and Santorum are among the few Republicans facing challenging statewide campaigns in states won by Democratic presidential candidate John Kerry in 2004. Both are pulling out all the stops as they try to revive the milk program.

Green is running to unseat Wisconsin's Democratic Gov. Jim Doyle; Santorum is lagging in the polls in his bid for re-election. Then there's Rep. Mark Kennedy, R-Minn., running for the Senate. Two weeks ago, he cast the decisive vote in the House to pass a $50 billion deficit reduction bill after receiving assurances that the milk program would get new life.

Their opponents in the milk battle aren't Democrats. The tricky politics of dairy policy pits region against region rather than one party against another. Republicans from states like California, Arizona, New Mexico and Idaho — whose farmers don't really benefit from the program — are leading the opposition, creating the GOP family feud.

Farmers from states where dairy herds tend to be smaller — such as Wisconsin, Minnesota, New York and Pennsylvania — benefit more from the milk program since it pays farmers only on the amount of milk produced by about 120 cows in a year. Western states with their generally larger herds benefit far less.

"Dairy policy isn't partisan," says Green. "As a Republican in the majority, I'd love it to be partisan. It's not. It's geographic, so getting the support for it is much harder."

Most lawmakers, in fact, don't have a strong opinion about milk policy. That means that those from states where milk is important often must play hardball to get party leaders' attention.

House Speaker Dennis Hastert, R-Ill., discovered this two weeks ago in trying to round up the last few votes he needed to pass the budget bill, a pillar of the GOP's agenda this fall.

The House version of the bill didn't contain the milk program extension. Renewing it for two years would have forced the Agriculture Committee to cover the $1 billion cost by cutting an equal amount from other farm programs or food stamps, a nonstarter for Chairman Robert Goodlatte, R-Va.

Scrambling for votes, Hastert wrote a letter to Green promising "to maintain a strong safety net for your dairy producers." That helped cement support for the budget from moderate Republicans from states such as New York and Pennsylvania. Green says he would have supported the budget even without Hastert's promise.

The Senate version of the budget extends the milk program, but only over stout objections from Western senators like Pat Roberts, R-Kan., who opposed it because of the resulting cuts in payments to other farmers.

Hastert's letter signaling that the House would bow to the Senate would seem to put the issue to rest. But Sen. Pete Domenici, R-N.M., one of the Senate's powerful "old bulls," is leading a battle against extending the milk program. And since he'll be an official negotiator for the Senate in talks on the budget, Domenici's objections can't be dismissed.

Domenici's state is home to huge dairy farms that produce lots of milk but receive relatively little benefit from the subsidy program. He says the program encourages overproduction in places like Wisconsin and Minnesota, which lowers prices for everybody else.

An Agriculture Department study issued last year found that not only do states with large farms not benefit as much from the milk program, they "may be disadvantaged by the program altogether" because it encourages oversupply.

"Extending MILC in its current form is unacceptable," Domenici said, "and I will oppose it vigorously."