Kirk might just be saber rattling. His political fate will depend on how far ahead of the Republican Presidential ticket he can run and how much his moderate brand in Illinois can resist a Presidential election year turnout.
If I recall, Illinois hasn't ousted a senator since 1998, when Carol Mosely-Braun lost re-election after a disastrous term. (To put it kindly). Before that, I think 1984, when Charles Percy (R-Illinois) was ousted.
Kirk is for gay marriage, pro-choice, and isn't that out of touch with the state. He should net a decent chunk of votes, especially Downstate and the Collar counties. I see Kirk winning 48-53% of the vote. Unless our GOP ticket completely collapses, Kirk has, starting out, a 50-50 shot.
Mark Pryor and Mary Landrieu were also in touch with their states. In fact, pretty much everyone had LA as "lean D" at the start of the cycle...
Landrieu was a tough incumbent who'd survived before. Nobody would seriously suggest that she is in touch with Louisiana today. Pryor was a little better off, but being a Democrat in the South is a political death sentence now.
