Head to Head of Clinton or Obama vs. McCain or Romney

http://www.electoral-vote.com/
has some really interesting poll results at the bottom of their current page:

These are for head to head matchups of the remaining 4 likely nominees.

Finally, Cook/RT Strategies just released some head-to-head polls for the
general election. Here they are.

Democrat Pct Republican Pct
Clinton 41 McCain 45
Obama 45 McCain 43
Clinton 48 Romney 42
Obama 50 Romney 41

If McCain is the GOP nominee, he beats Clinton but loses narrowly to Obama.
If Romney is the GOP nominee, it will be a rout.
But November is a LOOOONG ways away. A lot can change.