Chocola also said the plan didn't reach far enough.

"It moves us in the right direction," he said. "It’s more tinkering than reform, but it would be better than what we had now."

The Club for Growth, a deep-pocketed group that backs fiscally conservative Republicans, often gets involved in House and Senate primaries, sometimes against incumbents. The group has not endorsed in the presidential race.

Chocola said that Newt Gingrich's plan, which allows people to choose between the current system and a 15 percent tax plan, "is probably the most pro-growth and most bold."

He also criticized Rick Santorum's plan. "The problem with Santorum’s [plan] is he wants to pick winners and losers just like we do now by saying manufacturers don’t have to pick corporate income taxes," he said. "Santorum’s kind of a protectionist; his plan has some flaws as well."