COLUMBIA, S.C. — A new surrogate for Mitt Romney warned Saturday night that if Newt Gingrich is the nominee he could give Democrats united control of Congress.

Henry Barbour, a top Rick Perry fundraiser who endorsed Mitt Romney after the Texas governor dropped out, said Gingrich could not beat President Obama and would cost Republicans many House and Senate seats.

Barbour told The Hill that endorsing Romney and coming to his South Carolina rally was a "very easy decision" because of Gingrich, who he said would turn the presidential race from a referendum on Obama into "the adventures of Newt Gingrich."

"Newt would be a disaster as the nominee," he said. "He will put the House at risk. He will put our chances of taking the Senate down the tubes."

Barbour, who ran his uncle Haley Barbour's successful reelection campaign as Mississippi governor, warned that Gingrich would cost the GOP chances at some governorships as well, and could not beat Obama.

"He's too polarizing a figure to win the White House. He can't win independent voters and we can't win the White House without independent voters. He would be a disaster for our down-ticket candidates and our gubernatorial candidates."