CONSERVATIVE cable-news host Tucker Carlson is out at MSNBC and David Gregory – who made his reputation knocking heads with President Bush – is replacing him.

Gregory’s new show – to be called “Race for the White House” – will air at 6 p.m. starting next Monday.

He has had a long history of battling with press secretaries for President Bush, who have accused him of being partisan against the president, and a grandstander.

Carlson, who was a short-lived competitor on “Dancing with the Stars,” has anchored a one-hour nightly show on MSNBC for the last three years.

He will remain with the news network as a commentator on various shows.

Gregory will keep his current assignment as White House correspondent – and will continue filling in for Matt Lauer on the “Today” show.