Michael Bloomberg, the liberal mayor of New York, left the Republican party in what seems likely to be a prelude to a run at the presidency as an independent in 2008.

Now, can Michael Bloomberg win the presidency? No. I've written about this in detail previously and you can see it here, if you want to read about the difficulties of winning as a third party candidate.

So, if Bloomberg gets in and isn't viable, the only real question is: who would his candidacy hurt more? That's a complex question, especially since we don't know what all of his positions would turn out to be. But, here are some early guesses....

* The natural issue for a third party candidate would seem to be illegal immigration, but Bloomberg is pro-comprehensive immigration, just like all the top tier Republican and Democratic candidates, other than Fred Thompson. If Fred Thompson or another tough on illegal immigration nominee like Duncan Hunter were to win the nomination, Bloomberg would hurt the Democratic candidate. If both candidates are pro-comprehensive immigration, Bloomberg's entry would probably be a wash.

* Bloomberg is pro-abortion. Again, that would probably undercut the Democratic nominee.

* Bloomberg is Jewish and since Jews typically vote Democratic 70/30, he would probably draw more of them from the Democratic candidate.

* Since Bloomberg is from New York, you'd have to think he would have the potential to draw votes away from the home town girl, Hillary in New York State and perhaps in states like Florida, which have a lot of transplanted New Yorkers living there. If Rudy turns out to be the GOP nominee, this would probably turn out to be a moot issue.

* Bloomberg does have a reputation as a fiscal conservative, but he has raised taxes and is not in any way, shape, or form a small government guy. We're talking about a guy who banned trans-fats in restaurants. So, for that reason, he would probably have a lot of difficulty appealing to small government conservatives. Again, this issue would probably be a wash.

* Bloomberg hasn't talked a whole lot about foreign policy which isn't surprising, given that he's just a mayor, but the limited number of things he has said about the issues make him sound more like a Democrat than a Republican. So again, he would probably drain more support from the Democratic candidate.

Long story short, it's too early to say for sure whom Bloomberg would hurt the most given that we don't who the candidates will be and which issues will move to the forefront in 2008, but given that Bloomberg is well to the left of center, you'd have to think he'd take a bigger bite out of a Democrat than a Republican.