Voter dissatisfaction with Republicans and Democrats is at historic levels, and the tea-party movement is hoping to play kingmaker in the November elections. The country’s current breed of discontent is ideal for the tea parties, because economic concerns are foremost, allowing the movement to sidestep the divisions between its libertarian and conservative wings. As the elections near, however, voters will want to know where the party stands not just on the economy but on social issues. A perfect illustration is drug policy, where conservatives advocate continued prohibition but libertarians argue for legalization. Which way should the tea party lean when...