COLUMBIA--A conservative economic group is paying for a television ad criticizing U.S. Sen. Lindsey Graham for his support of an idea to increase the amount of income subject to Social Security taxes.

The ads from the Washington-based Club for Growth began airing across South Carolina starting Tuesday.

Graham, R-S.C., has received a lot of attention as he tries to broker a deal on Social Security.

While some of Graham's proposals, like private accounts, are supported by the Club for Growth, the group does not like Graham's idea of raising the income cap from $90,000 to $150,000 to help pay for the hefty costs of creating private Social Security accounts.

The group thinks raising the cap conflicts with conservative ideals of lower taxes and smaller government. The members want South Carolina voters to know they think the plan is a tax increase, said Henry McVicker of Shirley & Banister, the Virginia firm hired to roll out the spot.

McVicker said the Graham ad will run for enough time to make sure it is widely viewed. Its cost was not immediately available.

Graham's office released a statement Monday pointing out his support for changing Social Security has been known since before he was elected to the Senate in 2002.

"His opponents spent more than $3 million dollars attacking him for holding that view, but he didn't back down one inch. He wasn't intimidated then, and he's not going to be intimidated now," the statement read.

The ad is likely meant as a warning to Graham, since he doesn't face re-election for three years, Winthrop University political science professor Scott Huffmon said.

The Club for Growth has 9,000 members and raised more than $10 million for candidates in the 2004 elections.

The group gave Graham $2,500 when he first ran for Senate in 2002.