For what it is worth, here is the latest 2008 Presidential Poll from the Marist College Institute for Public Opinion.
The top five Democrats in the Poll are: Hillary Clinton, John Kerry, John Edwards, Joe Biden and Wesley Clark. The top five Republicans are Rudy Giuliani, John McCain, Condi Rice, Jeb Bush, and, drumroll, Newt Gingrich.
McCain beats Hillary by 12 points in a head-to-head match up.
If Jeb is included in the poll, they should have included Dick Cheney.