During a speech last month to Georgia law enforcement officials, President Bush opined that opponents of the stalled immigration reform bill "don't want to do what's right for America." If they only understood the bill's provisions, he implied, they would see the light. But, alas, they hadn't "read the bill" and could only "speculate" about its complex provisions. He warned them to stop trying "to frighten people."

These unscripted remarks unleashed a torrent of criticism from the president's political base. Conservative talk-show hosts, pundits, bloggers and grassroots activists seized on the criticism as an opportunity to educate Americans on the bill's many flaws. Constituent mail and phone calls poured in. Ultimately, a hardy band of conservatives forced Senate Majority Leader Harry Reid to pull the bill after two weeks of angry debate.

Last week, the president ventured to Capitol Hill to dine with Republican senators in a high-profile attempt to revive the bill. But he converted no one. With congressional leaders scheduled to consider other legislation guaranteed to further annoy and divide the president's supporters (e.g., reauthorizing the No Child Left Behind Act and approving the sovereignty-stripping Law of the Sea Treaty), the question arises as to whether the president's immigration dilemma -- having to thread the needle between openly hostile conservatives and the usual assortment of Bush-haters on the Left -- will be the norm for his remaining 18 months in office.

Several recent polls underscore the extent of his challenge.

According to a survey by the Pew Research Center, the president's overall approval rating fell six points between April and June (from 35% to 29%). But the drop was most intense among Republicans (from 77% to 65%), including conservative Republicans (from 86% to 74%), and Independents (from 34% to 22%).

Another poll, conducted by Gallup after Bush's Georgia speech, found a similar drop in his standing among GOP loyalists, where his positive rating hit a near-record low of 70% (alarms sound whenever a politician scores below 80% with his core supporters). According to Gallup, the only other time Bush's GOP approval rating was so low was about a year ago when -- you guessed it -- the Senate was angrily debating comprehensive immigration reform. Hmmm.

"It was the debate over immigration," pollster Scott Rasmussen confirmed last week, "that cost the president support among his base and pushed his approval ratings to new lows."

Political operatives are well aware that the disenchantment over immigration has settled primarily on Bush and those lawmakers who have led the charge in the Senate. Sen. Reid's approval rating sunk 7 points in a month, to a microscopic 19%. John McCain (R-Ariz.) fell in many presidential polls. Yet the national GOP emerged unscathed, and may even have benefited, from the turmoil.

A month ago, Rasmussen reports, Democrats enjoyed a 14-point advantage (47% to 33%) as the party best able to handle immigration. Following the Senate debate, however, the Democrats' advantage shrunk to only five points (40% to 35%). "Immigration," he concludes, "is now tied with taxes as the GOP's strongest issue" and is "the only issue on which unaffiliated voters trust Republicans more than Democrats."

What explains the intensity so many Republicans and Republican-leaning Independents bring to this issue? My guess is that this is yet another manifestation of the ideological divide that separates Red from Blue America. Because Republicans are more reflexively pro-American than their Democratic colleagues, they place a much higher value on U.S. citizenship and therefore are more likely to vigorously oppose policies they perceive as granting citizenship too freely, especially to lawbreakers.

For example, polls demonstrate that Republicans are more likely than Democrats to say they are "very patriotic" and more likely to see America as a place where "most people living in other countries would like to live." Also, by a 2-to-1 margin, Republicans believe "we should be willing to fight for our country … right or wrong." A majority of Democrats disagree. Finally, Republicans attach more importance to the rule of law than Democrats do. Republicans are much more likely to want to penalize employers who knowingly hire illegal aliens and banks that offer them credit cards.

The disenchantment with Bush can be summed up in an L.A. Times/Bloomberg poll, which asked Republican primary voters whether they want the next Republican nominee for president to continue Bush's policies or move the country in a new direction.

They opted for a new direction by the overwhelming margin of 65% to 27%.

Mike Franc, who has held a number of positions on Capitol Hill, is vice president of Government Relations at The Heritage Foundation.