I don't think many voters go through that kind of calculus before heading to the polls. A concentrated, focused effort like that would take coordination, e-mails from some party or campaign, and there would be a mighty backlash when those leaked out. Which they would. I could flit around the Web ans sign up for e-mail alerts from every candidate in every party. You gotta believe someone in Hallry's campaign gets Rudy's updates, and vise versa and et cetera.
Come to think of it, I'm half-tempted to set up a series of dummy e-mail accounts and sign up for every candidate's updates. Post them all to an anonymous blog. If a candidate is saying one thing to supporters and another to the public at large, he oughta get nailed for that.