Which candidate do you agree with on the issues?
Of course, there are other considerations besides issue agreement one should take into account when voting in primaries (experience, electability, charisma, character, what interest groups they are beholden to, what kind of people they surround themselves with, etc.) . But it is good to have some inkling of which candidates agree with you the most on some of these things.
Right now, I'm undecided as to who to vote for in the Democratic primary. The progressive blogosphere hasn't really coalesced around a candidate yet. It will probably not be Hillary Clinton, as I feel her foreign policy stances are too belligerent, and she has not been good about standing up to the Bush administration. I also feel she is part of the Democratic party establishment whose habits (reflexive "centrism" that plays into the hands of right-wingers, and a fear of the "dirty hippie" activist base of the party) I dislike and I feel are damaging to the effectiveness of the party.
It is likely that Clinton will be in a strong position once California has our primary (though who knows--at this time in the 2004 campaign Wes Clark and Howard Dean were leading), and I worry about the progressive vote being split among several candidates. So it is possible I will be shifting about a good deal. I have been very impressed with Edwards when he spends time talking about the poor in this country. He seems like the only high-profile politician who is doing so. But I am not committed in any way yet.