In his last State of the Union address, President Bush made a brief pitch for the beleaguered cause of immigration reform.

After telling Congress of efforts to secure the borders and step up enforcement, he observed: "We must also find a sensible and humane way to deal with people here illegally. Illegal immigration is complicated, but it can be resolved. And it must be resolved in a way that upholds both our laws and our highest ideals."

Mr. Bush was right. But because he has not been assertive enough in his presidential leadership, Lou Dobbs and other living shades of nativists have demagogued to death any talk of high ideals.

This is a national shame on several levels. The estimated number of illegal immigrants in this country is between 12 million and 20 million. Anti-immigrant propaganda to the contrary, it is clear that the vast majority just want to work hard and build a better life. For practical and humane reasons, deportation of so many millions is not a realistic option. For a country teetering on the edge of recession, it might even be economic suicide.

Yet the nation's borders need to be secured for reasons that are legitimate and have nothing to do with racism. Sovereignty is one. Security in the age of terrorism is another and so is upholding respect for the law. Beyond that, the unchecked growth of illegal immigration threatens to put excessive demands on America's resources.

Yes, the immigration issue is complicated and none feel the challenge more than the presidential candidates who must make sensible cases when angry voices are the loudest.

• John McCain, the presumptive Republican nominee, has a particular challenge. Among the top reasons hard-core conservatives don't like him is his record on immigration. Together with Sen. Ted Kennedy, the bogeyman of right-wing fever dreams, he co-sponsored reform legislation with a provision that would have put illegal immigrants on a road to eventual citizenship.

Since the bill's failure, the senator from Arizona has been more circumspect without completely repudiating the earlier effort. Now he is all about stressing the need to secure the border -- in short, first things first without much discussion of what would come second.

Asked in a debate whether he would vote for his old bill if it came up again, he avoided the question by insisting the situation had changed. "We are all committed to carrying out the mandate of the American people, which is a national security issue, which is securing the borders," Mr. McCain said.

• Mike Huckabee, the former governor of Arkansas, is not shy about opposing amnesty -- the populist position of the hour. He also strongly supports completing a border fence. According to his Web site, he would give illegal immigrants 120 days to register with immigration officials and then leave the country. Those who register and leave would have no penalty if they later applied to emigrate, but they would go to the back of the line.

The Democrats believe in some sort of amnesty, although they are hardly shouting the A word from the rooftops. Both also strongly support beefing up border security.

• Barack Obama frames the issue in the familiar, compassionate terms of bringing "people out of the shadows." As his Web site says, he supports "a system that allows undocumented immigrants who are in good standing to pay a fine, learn English, not violate the law and go to the back of the line for the opportunity to become citizens."

The Illinois senator would also crack down on employers who hire illegal workers and try to improve the immigration bureaucracy, which would lessen the burdens on legal immigrants seeking citizenship.

• Hillary Clinton, who takes pride in her efforts in Congress to help immigrant families, stumbled a bit in the campaign over the issue of whether illegal immigrants should be allowed to have driver's licenses before coming out clearly against it.

Still, she and Mr. Obama don't differ much on the issue. She would also provide a path to citizenship for illegal immigrants who have been living and working here without getting into trouble; she would require them to learn English and pay a fine. She would also crack down on employers who continue to hire or exploit undocumented workers.

The immigration issue has been too enflamed for Americans to expect a quick resolution. The major candidates start with the premise that the borders must be secured and, while that is the place to start, it's also the easy part. After that, it will be time to restart the discussion on a decent and practical way to bring those millions out of the shadows.