You've read it, heard it, tasted it, savored it, seen it in photo-op action: Want a "classic" or "authentic" Philly cheesesteak? Gotta go with Cheez Whiz.

Maybe it's time to melt that myth.

True, Whiz is king at Pat's and Geno's, those legendary South Philly sites at Ninth and Passyunk. During the Pennsylvania primary, Comedy Central's Stephen Colbert said their feud was fiercer than the Democrats' - and showed a sandwich dripping with Whiz.

Barack and Michelle Obama, as well as Bill and Chelsea Clinton, ate at Pat's - and had Whiz.

But pundits, pleez note: Whiz wasn't first historically, and it's no runaway favorite regionwide.

At John's Roast Pork, which serves up taste-test winners on Snyder Avenue, the processed cheese sauce isn't even served.

"I'm a cheese eater, sweetheart, and I love cheese, but Whiz is not cheese," says owner Vonda Bucci, 75. "It's a lot of grease and coloring."

"We won't do it. We will not carry Cheez Whiz," said Jack Mullan, 50, co-owner of popular Leo's Steak Shop in Folcroft. And customers never complain.

A recent Philly.com poll asked, "What cheese belongs on a cheesesteak?" and Whiz finished third. American edged out provolone after more than 5,700 votes were cast.

Even Geno's owner Joey Vento, 68, downplays Whiz. "To be honest with you, I've never eaten Cheez Whiz, and I'm the owner," he said. " . . . We always recommend the provolone. . . . That's the real cheese."

The yellow runny goo, though, is the top choice of his customers - the locals as well as tourists, he said.

Ditto at Pat's King of Steaks, where Whiz oozed its way into history, said owner Frank Olivieri Jr., 44.

Originally, the Philly steak sandwich, invented by his Uncle Pat in the early 1930s, he said, had no cheese.

By and by, cheese was introduced. "Customers got tired of eating with or without onions, just like my Uncle Pat got tired of eating hot dogs," Frank Jr. said.

American or sharp provolone? was the original debate, he said.

In the mid 1950s - not long after Cheez Whiz hit the market - his father, Frank Sr., began keeping some by the grill, and telling customers to try it.

"It worked well, it tasted good. . . . It caught on," Frank Jr. said.

Other places started "impostoring us," he said.

But not immediately.

Patent attorney Stuart Beck, 67, remembers American as the standard for steaks in the mid '50s and early '60s when he was a student at Overbrook High, and later at Drexel University.