Which leaves Democratic politicians and political candidates out on a pretty flimsy limb. Most of them reflexively back a comprehensive bill, and some of them (like Bush and a number of Republicans backing such a bill) have dismissed opponents as racists.

Most Democrats have also been backing bills extending various benefits to illegal immigrants, like the Dream Act for college education for illegals brought over as children. There are appealing arguments for such bills. But most voters reject them. And most voters certainly reject driver's licenses for illegal immigrants. That was one of the issues that led to the recall of Gov. Gray Davis in California in 2003.

The Republican presidential candidates have taken note. Only John McCain, a longtime backer of a comprehensive bill, stands apart, and he concedes that voters are demanding tougher enforcement. In the special congressional election in Massachusetts on Oct. 5, the Republican was able to hold the Democrat to 51 percent by stressing immigration as one of his two top issues.

Other Republicans are likely to echo that theme next fall. And the Democratic presidential nominee (unless Chris Dodd gets the nod) is going to have to explain why she or he believes it's a good idea to give illegal immigrants driver's licenses.

The last several Democratic nominees could have said that they're just taking the same position as their Republican opponent. The 2008 nominee won't be able to say the same of hers or his (unless McCain gets the nod).

"The centrality of illegal immigration to the current discontent about the direction of the country may be taking us back again to a welfare moment," write the shrewd Democratic strategists James Carville and Stanley Greenberg. Yup.