Last Wednesday, Rep. Lynn Martin, the Illinois Republican senatorial challenger, had a fund-raising visit to her state from President Bush. Last night, Vice President Quayle was scheduled to boost her campaign.

But in between, Martin announced that "I cannot and will not support the proposed budget agreement" that Bush and Quayle had blessed at Sunday's Rose Garden ceremony because "it is bad for seniors, bad for taxpayers and bad for the state of Illinois."

"It wasn't a hard decision at all," her campaign manager, Mark Schroeder, said yesterday. Nor, as it turned out, was it difficult for her opponent, Sen. Paul Simon (D-Ill.), to dump on the agreement his party's congressional leaders had framed and approved. He said the budget accord puts "too much of the burden on middle-income families and older Americans."

Simon was still reserving judgment on his vote yesterday but his rhetoric was nearly as tough as Martin's.

Although Senate leaders expressed growing confidence that a majority of senators from both parties would support the deal, Martin and Simon were part of a bipartisan wave of senatorial candidates who swiftly announced their opposition to the agreement that was hammered out after months of painful negotiation. The quick, negative reactions of the Senate candidates illustrated the gulf separating campaign politics from the realities of governing a country beset by a giant budget deficit.

The pollsters and campaign consultants on both sides said simple politics virtually dictated that stance for anyone in a seriously contested race.

"Anybody who is for it is probably a masochist," said Democratic pollster Harrison Hickman. "There are a hundred things in it to hate."

National Republican Congressional Committee Co-Chairman Edward J. Rollins said, "I would certainly not argue" with candidates who oppose the package. He said he expected virtually all GOP challengers to adopt that stance and expressed the hope that "my vulnerable incumbents will be left off the hook" when the administration tries to round up votes for passage.

The list of politically poisonous elements cited by political strategists includes proposed increases in Medicare premiums for the elderly, higher gasoline, cigarette, beer and liquor taxes, and cuts in politically popular health, housing, education, urban and farm programs.

A host of Senate candidates in close races quickly determined that these liabilities far outweighed any advantage to be gained in supporting the package, regardless of the economic consequences for the country. Democrats and Republicans, liberals and conservatives who face tough opposition in November, all found reasons to object.

Without exception, the Senate candidates premised their decision on substantive objections to the agreement. Some of the same objections came from House and Senate members with few reelection problems. But the political calculus for people in tough races was evident.

Last month, well before the final agreement was reached, Garin-Hart Strategic Research Group, a Democratic polling firm, argued in a memo to clients that a vote for a major deficit-reduction package carried serious political dangers.

Using a sample of 506 likely voters in a Midwestern congressional district, the firm found that "overall voters in this district say by 67 percent to 23 percent that they would oppose the budget plan" after its major elements had been described to them.

In one of the clearest statements of the political logic, the firm wrote: "Voting for a budget settlement . . . may be the most responsible course, but do not expect much credit from voters for doing the responsible thing. . . . If you vote for the budget compromise, you should recognize that many voters will resent it. The dominant feeling voters appear to have on this issue is: 'We did not create the deficit, we did not benefit from it, and it is not fair to put the burden of solving the deficit on our backs.' "

The candidates' comments seemed to reflect that judgment. "The budget plan," declared Ted Muenster, the Democratic Senate nominee in South Dakota, "is not a victory. It's largely an attack on the average American."

Rep. Hank Brown (R-Colo.), who is running for the open Colorado Senate seat against Democrat Josie Heath, denounced the plan as a "fraud. The estimates {of budget savings} are so flakey I don't think it's much to hang your hat on."

Some Democratic incumbents with serious reelection contests held their fire. Simon and Sen. Claiborne Pell (D-R.I.) took the judicious stance, while expressing distaste for key provisions. Sen. Carl M. Levin (D-Mich.) issued a one-sentence statement: "I'm going to give the complete package careful review."

Sen. Tom Harkin (D-Iowa), in a tortured statement, left open just a sliver of a chance that he will cast a "yea" vote: "Senior citizens and our family farmers will suffer disproportionately. More than half the cuts in entitlement programs will come from the Medicare budget. . . . Nevertheless, I recognize the bipartisan effort that went into this agreement, but I believe it is seriously flawed. . . . I will spend the next couple of days studying the agreement carefully."

Harkin's challenger, Rep. Thomas J. Tauke (R-Iowa), was less hesitant in making his decision. "I've decided to vote against it," he said in an interview. "It's a business-as-usual package. It is bad for Iowa and for the country."

In New Hampshire, both Senate candidates came out against the measure, but former senator John Durkin (D) sought to escalate the battle by calling on his opponent, Rep. Robert C. Smith (R), to "disinvite" Bush from a scheduled campaign appearance in New Hampshire for Smith on Friday.

Illinois candidate Martin lost her date with Quayle last night -- but not because she jumped ship on the budget agreement. Quayle stayed in Washington to help lobby for the package and promised Martin a makeup appearance.

While candidates were defecting right and left, the leaders of both parties rallied behind the agreement. Democratic National Chairman Ronald H. Brown told reporters, "I support the leadership position" and promised he would "not be critical of those who vote for the package," even if they are Republicans he would love to see defeated.

Brown and others suggested that the alternative of deep, across-the-board spending cuts and the resulting "chaos" would make the budget package seem preferable. But Democratic pollster Geoff Garin disagreed.

"If it {the budget agreement} goes down," he said, "it would be further proof to people that the system doesn't work. But that generalized anger is small compared to the personalized anger {an incumbent might face} for an individual vote" for the package.

The reaction pointed up what many observers have noted as the growing gap between campaign politics and governing. Some campaign advisers said that they had to distinguish between the country's interest in having the deficit reduced and their clients' desire to reduce their political risks.

Hickman tacitly acknowledged this when he was asked what counsel he was giving to candidates. "The Republic is better off if nobody asks me," he said.

Political researcher Bruce Brown contributed to this report.