primary voteing

I have  a riddle for you, this is only relevant for Dems at this point in time, but the riddle applies to republicans in four years, or abstractly now too. I am not so much interested in literal application of the answer, but a general theory.

if you are a leftist, does it do more to further your political agenda to register as a republican in the primary and
A) vote for the most moderate candidate, and try to shift the discussion towards your worldview?
or
B)vote for the most unelectable candidate, in an attempt to make the general election easier for obama?


like i said, i am interested in how you think this would work. if you are a right wing guy, just pretend its four years from now, and we can talk about this strategy in more general terms.

thanks.

People on both sides have done both since the inception of democracy.  I personally vote in republican primaries and vote for more libertarian candidates Ron Paul last election, Gary Johnson this one.  But since they never win the primary I usually vote democrat in the actual election.