AUSTIN -- Wes Riddle and Roger Williams, the surviving GOP candidates for the 25th Congressional District, propose abolishing the Internal Revenue Service, find their political inspiration in the Bible and the U.S. Constitution, and say defeating President Barack Obama is essential to the nation's future.Agreeing on most issues, the opponents in the primary runoff emphasized their different backgrounds during a forum Tuesday with the Republican Club of Austin.Riddle reminded the audience of about 60 that he founded the Central Texas Tea Party and retired as a lieutenant colonel after a 20-year Army career, establishing his bona fides as an advocate for limited government spending and a strong military.He said he would "stand up and restore the Constitution and put that man back in the box. We do not need to compromise with our own destruction."Williams, a former Texas secretary of state and owner of a Weatherford car dealership, introduced himself as a "Christian, conservative business guy.""We need businesspeople more than ever to go to Washington and make these business decisions instead of these political decisions," Williams said. "We need somebody to fight for small businesses."The candidates emerged from a 12-way primary to advance to the July 31 runoff -- Williams with 25.1 percent of the vote, Riddle with 14.6 percent.The 25th District runs from Burleson to Austin. Tuesday's forum opened with a question about proposed changes to Social Security."Social Security is a mess," Williams said, adding that he would propose three changes: make workers 45 and younger eligible to draw payments after age 70, allow younger workers to invest a portion of their Social Security payments, and end diversions of Social Security money into other programs.Riddle said younger voters should be allowed to opt out of Social Security and invest in private alternatives. "It's clear that when Social Security went into effect, things were very different," he said, adding that President Franklin D. Roosevelt never intended it to be a permanent program.On taxes, Riddle said he favors a flat tax, based on a percentage of earnings without deductions, similar to what Gov. Rick Perry proposed in his presidential campaign. He would also cut corporate tax rates, allow companies to write off new equipment and allow multinational businesses to return profits to this country tax-free.Williams said he supports a flat tax or a national sales tax. He also favors eliminating the inheritance tax and cutting taxes on capital gains, dividends and corporate income.