If you are a fanatic about what your favourite Republican or Democrat is looking like in the eyes of John Q. Public, then you will love these links.
Here's the Democrats
Here's the Republicans
And here's the Democrats vs. the Republicans in a general election.
Looks like Giuliani would have the best shot to knock off the Dems. In the meantime, it's a toss up and no clear cut leader emerges from the democrats. Almost all of the top 4 win by similar margins over their Republican counterparts. In fact, I was astonished to see Gore wasn't ranked somewhat higher in these polls.