LAS VEGAS (AP) — Herman Cain is defending his tax plan a day after his Republican rivals assailed his 9-9-9 proposal in a presidential debate.At the Western Republican Leadership Conference on Wednesday, Cain told the audience that his plan will throw out the current tax code. He says his opponents want to build on what's already in place.Rick Perry says he wants to throw out the tax code and replace it with a flat tax. Mitt Romney wants to make less dramatic tax changes.Cain said his opponents, including former Pennsylvania Sen. Rick Santorum, were too focused on what kind of plan could pass Congress. He said he wasn't worried about Congress. That's the "difference between a politician and a problem-solver," Cain said, which is how he's positioning himself.