Businessman and two-time presidential candidate Steve Forbes is backing Rick Perry's presidential bid.

Forbes's support for Perry stems primarily from the Texas governor's support for a flat-tax system, which Forbes drilled as his primary campaign theme in 1996 and 2000.

"With firm leadership which Rick Perry will provide — which is why I'm endorsing him for president — I think this will be a winning issue," Forbes said on Fox News.

On Wednesday, Perry told Republican activists in Las Vegas that he would introduce a flat-tax proposal, but did not reveal any details. Those details are expected Tuesday, when Perry unveils his plan in South Carolina.

Forbes has been advising Perry, but it remains to be seen how closely Perry's plan will mirror what Forbes proposed when he ran for president. Forbes favored a 17 percent flat rate with an exemption for annual incomes under $36,000.

“Steve Forbes is a well known fiscal conservative, and provided strong support and advice throughout the process of drafting my economic and jobs plans,” Perry said in a statement. “I am honored to have Steve’s endorsement of my candidacy for president.”

Perry's call for a flat tax comes on the heels of rival Herman Cain's rise in the polls, where he has usurped the front-runner status Perry nabbed after entering the race in August. Cain has made his 9-9-9 plan for flat income, sales and corporate tax rates his singular buzzword for the 2012 campaign.

Yet Cain's plan has come under attack on both sides, with Democrats arguing it unfairly burdens the lower class and Republicans arguing the 9 percent national sales tax adds a new and unnecessary revenue stream for the federal government.

Cain has responded by tweaking the plan to allow an exemption for those living in poverty and for economically distressed areas. But every time Cain unveils an additional caveat, the plan's simplicity — its most appealing element — is blunted.

Forbes signaled that Perry's plan would not include the new sales tax that conservatives have hounded, which he said would make the plan "even more appealing."