A single poll has seemingly catapulted him from celebrity status to presidential threat. Journalists are poll junkies, and nothing gets their adrenaline pumping like fresh numbers—especially if someone famous is involved.So when Thursday’s NBC/Wall Street Journal survey had The Donald in second place among Republicans—at 17 percent, tied with Mike Huckabee and four points behind Mitt Romney—he crossed some invisible threshold, from impossible to plausible.Except I think most of my fellow pundits know better. That number reflects name recognition for a zillionaire playboy. It may also reflect a general sense that Trump is a take-charge businessman who would know something about fixing the economy.But most of all, it reflects Trump’s recent television blitz—where he has talked far less about his business acumen than about Barack Obama’s birth certificate, again and again. And the media just keep giving him a platform for this nonsense because Trump is good box office. He boosts the ratings. And there’s a sense that birther conspiracy theories are hot-button stuff, even if they are, inconveniently, disproved by the facts.So Meredith Vieira gives The Donald 10 minutes on Thursday’s Today show, and doesn’t object when he says of Obama: “His grandmother, in Kenya, said he was born in Kenya and she was there and witnessed the birth.”Not even a “really? When and where did she say this?”Chris Cillizza’s theory, on his Washington Post blog, is that “confrontation sells.” But don’t we in the MSM have a greater responsibility than to put on flat-earthers and say that “many scientists disagree”? Vieira pressed Trump on why he is pushing the birther line, but not on the claim about the grandmother.I don’t know why Trump is going down this road, since he could get plenty of attention with other lines of attack. But there was a hint in the NBC sitdown. Trump’s Celebrity Apprentice (a “great show,” he assured us, with “phenomenal ratings”) runs until June. If he declares for president now, he said, NBC would be forced to take the show off the air. So he has to wait.I doubt he’ll run and open up his business career and love life to journalistic scrutiny; he has done this tease before. He flirted with seeking the Reform Party nomination in 2000. So Trump climbing in the polls—wow, second place!—may be fun for reporters who’d rather not be delving into the complexities of Paul Ryan’s Medicare voucher plan. But anyone who believes Trump is going to drag himself along the grueling path to the White House should be fired, maybe on national television.