Phil Griffin knew it would happen, he just didn't think it would happen this quickly. On Friday night, MSNBC's Countdown with Keith Olbermann was the top-rated cable news show in the 25-54 demo. That means Olbermann beat his cable rival, FNC's The O'Reilly Factor and its host Bill O'Reilly. That's a first.

"The real insight I had was over the summer," said Griffin, the NBC News senior VP who manages the Today show as well as MSNBC. Griffin tells TVNewser, Olbermann "maintained his core audience, so when the mass viewers came back after Labor Day...it's just surprising it happened so quickly."

O'Reilly and all the FNC primetime programs still dominate the total viewer numbers. So why is the demo win such a big deal? "It's everything, the demo is everything. It's where we make our money," said Griffin.

This is going to be a busy autumn for MSNBC. In a few weeks, the cable net's employees will move out of their New Jersey offices and move in with their broadcast counterparts in New York City. And the Olbermann bump helps. "For years MSNBC struggled to find someone to be the tent pole and lead the way," Griffin says. "In 11+ years, I don't think there has been a better moment."

Griffin should know, he helped start MSNBC and watched as FNC shot past CNN to #1 where it remains today. And he says Bill O'Reilly rightly gets a lot of the credit. "O'Reilly did it for Fox in 1999, and helped take it to where it is today." But, he adds, "It's clear now, it's a two-person race."

When asked to comment for this story, Fox News spokesperson Irena Briganti wrote, "Does Mediabistro know you're on two payrolls — MSNBC's and theirs?"

(of course, I haven't been on MSNBC's payroll since I left the company in January.)