The most interesting political matchup right now is between former Massachusetts Gov. Mitt Romney and former New York City mayor Rudy Giuliani because they're running for the same voters. Over the last 20 years, the largely accurate conventional wisdom has been that the GOP could not nominate a pro-choice politician, just as the Democratic Party could never nominate a pro-life one. Some Republicans, including Ronald Reagan and the elder George Bush, had to move from a middle-of-the-road position on abortion to the right-hand guardrail, while some Democrats who once leaned to the pro-life side of the road had to...