I like Herman Cain very much, and the only thing holding me back from supporting him 100% is his FairTax position (FairTax is a ready-made DNC talking point), but by your logic...
Ronald Reagan was a tax hiker because he tolerated George Bush, and a pro-choicer because he considered running with Gerald Ford.
No sale.
But he DID run with the pro choice George H.W. Bush, who had to have an abortion lobotomy and become pro life as a condition of getting the veep spot.