My daughter was born in Los Angeles County on Sept. 4, 1990. I know this because I was there. Should that not be proof enough, I also have her birth certificate.

We requested it years ago and received a document that looks nothing like the ones I have for my folks, with names and parentage typed in tiny boxes. By contrast, this was a computer-generated abstract with my daughter's data neatly printed on it. We asked why we couldn't get a "real" birth certificate and were told this one "is" real; this is how they do it now. Indeed, the inscription on the certificate proclaims: "This certified document is a true abstract of the official record filed with the Registrar-Recorder."

We used that document to get my daughter's Social Security card, so I figure a "true abstract" is good enough for the federal government. But evidently, it's not good enough for Stefan Cook, Orly Taitz, Rush Limbaugh, Philip Berg and Lou Dobbs.

Barack Obama, you see, has a birth certificate much like my daughter's, documenting his birth in Hawaii on Aug. 4, 1961. He's made it available online, just a Google search away.

But that didn't satisfy Cook, a U.S. Army reservist who refused to deploy to Afghanistan because, he recently explained, his commander in chief is not qualified to be his commander in chief. Or Taitz, the Russian-born lawyer who represents him. Or Limbaugh, the radio loudmouth who tells his listeners the president has no birth certificate. Or Berg, who has made a career out of suing the president over this "issue." Or Lou Dobbs who, while professing his belief that Obama was born in this country, has kept up a drumbeat demanding that he prove it.

As if he had not already. The "birthers" movement — people who claim Obama cannot be president because he isn't a citizen — has proved hardier than cockroaches in its ability to survive the passage of time and repeated collisions with reality. It is, if anything, more visible now than at any time in the year or so since first it surfaced. It even includes a handful of GOP lawmakers.

Yours truly lacks the acumen to calculate how stupid you'd have to be to believe there is a shred of a shred of a piece of a fraction of validity to their claim. With the untold fortune Hillary Clinton, John McCain and others spent researching Obama, we're supposed to believe it took Orly Taitz to dig out this bombshell? And what of the birth announcements in two Honolulu newspapers, heralding Obama's arrival? Did he send somebody back to '61 in a time machine to plant them?

Unbelievable.

And yet, believed.

Last month, GOP Rep. Mike Castle of Delaware was booed and shouted down at a town hall meeting because he dared vouch that the president is a citizen. If I were of that endangered species, the thoughtful conservative, I would find that deeply troubling.

And I'll save you the trouble: No, the left is not free of lunacy. Somewhere out there, somebody still thinks George W. Bush had the Pentagon bombed on Sept. 11. But the Democrats usually keep their loons off to the side where they are pandered to, yes, but not allowed to run the show. For Republicans, though, lunacy has "become" the show, a circus of extremism that now defines them. In it, Obama is an undocumented worker, Sonia Sotomayor is a Klanswoman, Saddam Hussein green-lighted the Sept. 11 attacks, and no one dares dissent for fear of the great and powerful Rush.

For a generation, the GOP has tolerated and encouraged this estrangement from reality because it played well at the ballot box. Rep. Castle's experience suggests the cost may now outstrip the benefits. Because the cost is the specter of a party rendered ridiculous — and irrelevant.

You have to ask yourself: How far from reality can you wander before you can't find your way home again? If conservatives aren't careful, they may soon find out.