Aides for several Republican senators reported a surge of calls and e-mail messages from constituents ridiculing the rebate as a paltry and transparent effort to pander to voters before the midterm elections in November.
"The conservatives think it is socialist bunk, and the liberals think it is conservative trickery," said Don Stewart, a spokesman for Senator John Cornyn, Republican of Texas, pointing out that the criticism was coming from across the ideological spectrum.
Angry constituents have asked, "Do you think we are prostitutes? Do you think you can buy us?" said another Republican senator's aide, who was granted anonymity to openly discuss the feedback because the senator had supported the plan.
Conservative talk radio hosts have been particularly vocal. "What kind of insult is this?" Rush Limbaugh asked on his radio program on Friday. "Instead of buying us off and treating us like we're a bunch of whores, just solve the problem." In commentary on Fox News Sunday, Brit Hume called the idea "silly."
The reaction comes as the rising price of gasoline has put the public in a volatile mood and as polls show that cynicism about Congress is at its highest level since 1994.
Still, Eric Ueland, chief of staff to Senator Bill Frist of Tennessee, the Republican leader, whose office played a main role in pulling the proposal together, said the rebate was an important short-term step in a broader array of measures that began with last year's energy bill. Constituents "believe government ought to step up to the plate rather than loll around in the dugout," Mr. Ueland wrote in an e-mail message on Sunday.
After members of Congress returned from the spring recess, when they got an earful about gas prices above $3 a gallon, they raced to propose solutions that might take effect before the elections. Democrats were pushing for a 60-day suspension of the federal gas tax of 18.4 cents a gallon, and the Senate Republican leadership settled on the rebate.
Those leaders and Finance Committee aides said many Republicans opposed the Democratic plan because they feared that oil companies, which pay the gas tax, would not pass savings on to the public, or that the laws of supply and demand would push the price up again.
There was also the probable opposition of House Republicans, who have been reluctant to jeopardize the flow of the gas tax revenue to the highway trust fund that underwrites road and bridge projects.
"Our folks thought it might amount to nothing for consumers," said one aide who was granted anonymity to discuss internal leadership deliberations.
Under the proposal, $100 checks would be sent late this summer to an estimated 100 million taxpayers, regardless of car ownership. Single taxpayers with adjusted gross incomes above about $146,000 would be ineligible for the checks, as would couples earning more than about $219,000. The $100 figure was determined by Mr. Frist's office, which calculated that the average driver would pay about $11 per month in federal gas taxes over nine months.
The rebate was the signature element of a broader Senate Republican leadership plan announced Thursday that included new incentives for the oil industry to increase its refining capacity and for consumers to buy hybrid cars. It would open the Arctic National Wildlife Refuge in Alaska to drilling and would impose an accounting change forcing oil companies to pay higher taxes on fuel sold from stockpiles.
The proposal would also give the executive branch new authority to set fuel standards for cars, an idea that will get a hearing in the House this week.
David Winston, a Republican pollster who advises the Senate Republican leadership, called the rebate an intuitive way to show voters that Republicans were on their side. "It is like putting the American family budget ahead of oil company profits," Mr. Winston said. "How do you help the American families out? Well, give them some money."
But disapproval started flowing in almost as soon as the idea surfaced, said aides in several Republican offices. One senior aide to a Southern lawmaker said the calls were surprisingly harsh. Some complained that the rebate would amount to only two fill-ups at the gas station.
Even though some voters have been outspoken in their opposition to the $100 rebate, Democrats still want credit for being the first to think of putting money back in taxpayers' pockets. A few days before the Republicans went public with their plan, Senator Debbie Stabenow, Democrat of Michigan, proposed a $500 rebate plan, a figure that she said was more commensurate with how much the higher gas prices will cost Americans this year.
Ms. Stabenow also criticized Republicans for linking the rebate to oil drilling in the arctic refuge.
Republicans know that drilling in the refuge "is highly controversial and not going to happen," Ms. Stabenow said. "I question their sincerity in putting this forward."
When the Republican program might reach the Senate floor is still uncertain. Mr. Frist had suggested that he might try to attach the plan to the emergency spending bill the Senate is debating, but aides said that was now less likely and that Republicans might ultimately bring their proposal forward on its own.
On television news programs on Sunday, several Republicans emphasized the need for long-term solutions and played down the rebates. "I don't think much about the $100 rebate," Senator Trent Lott, Republican of Mississippi, said on "Late Edition" on CNN. "We're going to have to produce more domestic oil, natural gas. We're going to have to build pipelines, liquefied natural gas plants."
Senator Lisa Murkowski, Republican of Alaska, struck a similar note on the CBS program "Face the Nation." "I don't think it's a real answer," she said. "It's a temporary Band-Aid. I don't think that it's, again, the long-range solution."
But in his e-mail message, Mr. Ueland, the chief of staff to Senator Frist, dismissed the accusations of pandering as the inevitable price of taking any action. "It's the way of the world to dog Washington when members respond to constituent concerns, but to be responsive is part of how the system is designed."