“The resistance, the angst of the people, is legitimate,” said Lott, R-Miss.

Senators from Oregon to Georgia echoed Lott's rueful apprehension that promises to deal with illegal immigration have slammed into a wall of public cynicism, especially among conservatives in both red and blue states.

There is widespread suspicion, lawmakers acknowledge, that Congress and the White House will fail again to fix a problem the federal government first said it would solve back in 1986 with a landmark law that combined amnesty with a border buildup and crackdown on employers who hired illegal immigrants.

“They're frustrated, angry and cynical,” Arizona Republican Sen. Jon Kyl said yesterday of many of the voters in his state. “The question they always ask is, 'Why should we believe you're going to enforce a new law if you're not going to enforce the existing law?' ”

Some 2.7 million illegal immigrants received amnesty under the 1986 law, but the promised crackdowns at the border and in the workplace fizzled. After a brief lull, the illegal flow across the border resumed. It has been accelerating ever since, with the illegal-immigrant population currently estimated at 12 million – twice the estimated total in 1986.

“Passions run very strong on this,” said Sen. Ron Wyden, D-Ore., reporting on town meetings he had back home over the Memorial Day recess.

“The Congress and the president don't have credibility,” added Sen. Johnny Isakson. The Georgia Republican invented the legislation's “triggers,” which were an attempt to win public confidence in the government's promise to stem illegal immigration after so many similar promises have gone unfulfilled in the past.

The triggers require more Border Patrol agents, vehicle barriers and high-tech surveillance equipment to be in place along the border before the permanent legalization program kicks in with the distribution of green cards. However, illegal immigrants would be eligible immediately for temporary visas allowing them to stay in the country and work in the meantime.

Proponents of the bill are aggressively selling the triggers as a fail-safe.

Bush declared recently that the bill's enforcement provisions would “solve this problem once and for all.” Other proponents, including Sen. John McCain, R-Ariz., have made similar promises.

But those reassuring words have not been enough to inspire confidence among critics of the bill, in part because they come after decades of similar failed promises.

The federal government has spent tens of billions of dollars on border enforcement during the past 25 years. There have been repeated crackdowns, with ever more resources being thrown into the battle to control the border, including large annual increases in the size of the Border Patrol. Bush said the government spent $10 billion on border enforcement last year alone.

Nonetheless, the nation's illegal-immigrant population is increasing at an annual rate of half a million.