What if it turns out we wasted all this time breathlessly following Rudy Giuliani’s meteoric rise to the front of the GOP primary pack, just to have former Sen. Fred Thompson (R-Tenn.) get in the race, knock Rudy’s celebrity socks off and turn America’s Mayor into just another also-ran?

It’s likely, but since that hasn’t happened, let’s ponder this: Giuliani’s support is soft and thin. Get any true Red Republican to talk about Rudy’s appeal and they weave caveats in and out of the conversation with lawyerly precision. Untested, three wives, socially liberal, terrible temper, the pre-911 tenure in New York — the list is long. When Giuliani campaigned in Iowa this week the reception was courteous but the crowds weren’t exactly crushing. He tried to tell Iowans that everybody is the same no matter where they hail from, but it was plain to see Rudy is no rock star to these heartland caucusers, at least not yet. That could prove dangerous in other states down the road.

And once he gets down the road, how will the primary faithful digest the fact that Giuliani has told a grand jury he simply doesn’t recall being told Bernard Kerik had ties to a company linked to organized crime. He was only Giuliani’s friend, close associate and police commissioner, so when a top staffer told Rudy that Bernie was doing business with crooks it must have been information so routine and typical that Giuliani quickly forgot it. Note to Giuliani: So far 2007 hasn’t been a good year for memory problems; just ask Scooter Libby and Alberto Gonzalez.

Rudy’s star power makes sense in a divided party and a weak field. But once everyone has his or her eyes on him, especially if Thompson becomes an option, the bright lights could be brutal.