KATIE Couric on CBS’ “Evening News” suddenly seems to have a real shot at dethroning NBC’s “Nightly News” from the top of the ratings heap.

With only three weeks to go until Couric takes over the anchor desk from Bob Schieffer and Dan Rather, the network evening-news ratings race is nearly neck and neck and neck.

But CBS News executive producer Rome Hartman believes major ratings shifts take place at a snail’s pace and doesn’t want to set expectations too high.

“Let’s be realistic,” says the longtime “60 Minutes” producer who took over the “Evening News” last year.

“History demonstrates that even when there’s a dramatic overhaul of broadcasts, change is a long time in coming, almost glacial,” Hartman says.

“I think the expectation that we’re gonna vault ahead of everyone and leave them in our dust is nuts,” he says.

“That said, are we excited about our prospects? Yes,” he says.

A major shift in the pecking order of the nightly newscasts would be something akin to a re-alignment of the planets – since the news-watching habits of viewers are among the hardest to change.

Nevertheless, the reigning champ, “NBC Nightly News with Brian Williams,” is starting to slip after nearly a decade on top – just enough to open the door to all sorts of possibilities.

For the year to date, NBC is down about 6 percent to about 9.12 million viewers.

CBS, meanwhile, under the surprisingly popular anchoring of Schieffer, has seen its ratings climb about 4 percent to roughly 7.39 million viewers.

And ABC’s “World News” anchored by Charles Gibson is down about 9 percent.

Katie’s chance

Ratings change from last year in net news

NBC CBS ABC

down 6% up 4% down 9%

9.12 m 7.39 m 8.12 m