PATRICK BUCHANAN, COMMENTATOR AND former presidential candidate, looked over the issues on the political agenda in 2006 and liked what he saw. It was a paleoconservative's delight. There was the Dubai ports deal, rejected by a congressional uprising part nationalistic, part isolationist. There's immigration, soon to be debated on the Senate floor and always high on the paleocon list of concerns. Excessive government spending, a worry of all conservatives but especially paleocons, is a major topic this year. And the intervention in Iraq and President Bush's crusade for democracy face sharp criticism, with paleocons in the lead among the critics.

It's a paleo moment in America. "It's a little bit late," Buchanan says. He'd rather it had occurred in 1992 or 1996, when he ran for the Republican presidential nomination, or in 2000, when he ran as the Reform party candidate. Chances are, the moment won't last. But it's a moment that could be politically painful for the president and harmful to Republicans in the midterm election in November. The paleocon message is not an electoral winner--unless you believe voters are eager to hear ideas that are gloomy, negative, defeatist, isolationist, nativist, and protectionist.

Buchanan is the big dog among paleocons. His message, were he to run again for president, he told me, would be: "Secure the borders, stop exporting jobs, and bring the troops home" from Iraq. I'm afraid many would interpret that message: Keep Mexicans out, forget free markets and free trade, and shrink America's role in the world. That's not an optimistic message.

It's not that these views are illegitimate. They're part--a small part--of the broad conservative coalition in America. And paleocons themselves are easily gathered under the big tent of the Republican party. The problem comes when they influence the party in ways that threaten the narrow Republican majority.

And they do this in several ways. One is to attack Bush on issue after issue. This weakens the Republican base and, potentially at least, reduces voter turnout. Republican voters dismiss criticism by Democrats or the media, but they pay attention when other Republicans zing Bush, or when they attack congressional Republicans, for that matter.

A larger threat is the paleocon influence on one of the touchiest issues, immigration. Here, their thinking is reflected in the anti-immigrant rhetoric of some congressional Republicans. And it is such thinking that imperils the gains made by Republicans among Hispanic voters.

In the immigration bill passed by the House last December, there was a distinct nativist streak. It calls for the raising of a 700-mile fence along America's southwest border with Mexico and for stepped-up border security in general. It was Buchanan who popularized the fence idea, and now a Republican senator intends to propose a fence along the entire border, from the Pacific Ocean to the Gulf of Mexico.

How would such a fence play politically? Well, it's a horrible symbol, one that clashes with the welcome mat laid out by the Statue of Liberty in New York Harbor. More important, it says to Mexican-Americans: We don't want any more people like you coming into our country.