Here is a simple scenario. John McCain and Hillary Clinton both win the major party nominations in 2008. Simply for the sake of the scenario Hillary Clinton manages to win the Iowa Caucus and New Hampshire and gains a financial advantage over Senator Obama, thus allowing her to win big on the February 22 Super Tuesday contests. By April 2008 McCain and Clinton have the nominations sewed up.
Senator Clinton selects Ohio Governor Ted Strickland as her running-mate. McCain taps Mike Huckabee as his running-mate to try and offset the Clinton appeal in the South (which I think polling showed Hillary Clinton was doing fairly well in the upper south). Everything happens like it did back in 2008. The banking system still collapses in October 2008.
My map:
Hillary Clinton/Ted Strickland (D): 374 EV; 53% of the popular voteJohn McCain/Mike Huckabee (R): 163 EV; 47% of the popular vote