The Club for Growth, an influential anti-spending group, is warning its followers that potential presidential candidate Donald Trump is a wolf in sheep's clothing - calling him just another "tax-hiking liberal" and a "king of protectionism" who doesn't deserve conservative support in the next election. Mr. Trump has flirted with a presidential bid for several weeks, leveling stiff criticism of the Obama administration and riding doubts about the president's birth certificate, reviving the so-called "birther" controversy that many have considered a dead issue.