SoxFan, good one. The high level strategy is to pin the Repubs down on what they believe. The win-win is that they either alienate the conservative base, or they alienate any possible centrist voters. Either way, it limits their votes. And if they refuse to answer, the Dem candidates can focus on that. What is Mr. X trying to hide...?
The success of Brown in Massachusetts is that he had his cake and ate it, too. He kept the conservative base who thought he would vote conservative, and he kept the centrist voters who thought he would vote centrist. But he obviously can't vote both ways - he just successfully convinced both sides into believing in a contradiction.
Dems can't let Repubs get away with this again.