Sen. Jesse Helms (R-N.C.) yields to no one in his zeal to cut the budget, but he draws the line at sacrificing tobacco subsidies. "In North Carolina," Helms explains, "tobacco isn't a commodity, it's a religion."

Sen. Warren Rudman (R-N.H.), a newcomer, is pledged to sacrifice even home state sacred cows, but chokes on the idea of slashing fuel assistance, a new and expanding federal program that heavily benefits frost-bitten New England. He says fuel assistance is "a matter of survival."

Even on the House and Senate Budget committees, where spending restraint is part of the job description, there seem to be limits to how far a politician can be expected to go.

No senator wants to reduce the deficit more than Pete V. Domenici (R-N.M.), the Budget Committee chairman. But Domenici comes from ever-thirsty New Mexico and says that, while there is a need for reform in the rivers-and-dams financing system, there is an even greater need for water in the West. There will have to be more money in the budget for water projects in the next decade, not less, Domenici says.

These are some of the early warning signs from Capitol Hill as Congress hunkers down to receive President Reagan's proposals for spending cuts, which some lawmakers who have had a preview describe as nothing short of "mind-boggling."

There is a loud clamor for budget cuts in Congress, even more so this year, when Congress tried to balance the federal budget, only to be put off by the effects of the recession, inflation and high interest rates. Even then Congress managed to approve an unprecedented "reconciliation" package of $8.2 billion in spending cuts and revenue-rising measures.

With the antispending message of the Nov. 4 elections still etched in members' minds, and with "uncontrollable" costs from open-ended entitlement programs threatening to send the budget deficit toward the $100 billion mark, sentiment is strong for even more retrenchment this year.

The problem is where to cut -- a dilemma reflected in a little ditty that Sen. Russell B. Long (D-La.) came up with years ago to explain the difficulties of writing tax law. "Don't tax you. Don't tax me. Tax that fellow behind the tree," was the way it went. Just substitute the word "cut" for "tax" and the problem for this year becomes clear.

It is enhanced by the fact that many of the easy cuts already have been made in programs ranging from food stamps, where free-riding college students were largely disqualified last year, to the water projects that were put on hold by former president Carter.

The problem is not that Rudman is wrong about fuel assistance (who wants poor people to freeze to death?) or that Helms and ranking Budget Committee Democrat Ernest F. Hollings (S.C.), also from a tobacco state, cannot make a case for the economic benefits of tobacco subsidies (which, they say, return more to the Treasury in taxes than they take out). The problem is that few politicians are willing to suffer unless they have plenty of company, and maybe not even then. And there is little chance that someone like Rudman can be convinced that tobacco subsidies are as important as fuel assistance.

The difficulty of achieving specific big-bucks cuts was illustrated dramatically last week when word was leaked that Office of Management and Budget Director David A. Stockman was proposing large cuts in foreign aid -- sending tremors not only through the foreign policy establishment but threatening to mobilize subsidiary constituencies such as farmers who like to sell their products abroad. The cuts likely to be proposed in the food stamp program face a similar pincer response from farm and welfare constituencies.

A similar lesson was learned last year when budget-cutters tried to save about $750 million by doing away with one of the two yearly cost-of-living increases in pensions to federal retirees. The retirees, who can be found in just about every member's district, fought back and won, and some members still are wincing at the retribution delivered at election time to those who voted for the cutback.