If this happened in the UK, it would probably help Labour more than the Tories, but the BNP might get a lot of "spite votes".
In any case, I oppose. It's too authoritarian.
In truth, I would suspect the Democrats would ultimately benefit from this. The Republicans are masters of keeping their voters loyal, but the Democrats have much easier ideas to sell.
"You want everyone to have health care? Then vote Democrat! You want Social Security when you are older? Vote Democrat! You want to end the Iraq war? Then vote Democrat on November 4th!"