Inhofe is easily beatable. Oklahoma may be very Republican, but we are also very Democratic. Inhofe is VERY unpopular in Oklahoma, and there is a possibility, albeit slight, that he might even get knocked off in the primary and not even make it to the general election. Think about it. Eastern Oklahoma, a very Democratic region, is growing. Western Oklahoma, a fairly Republican area, is holding steady. Oklahoma City is rapidly growing and is moving left of the far right.
I predict a Democratic pickup in 2008 in Oklahoma and another one in 2010.
DNC Chairman Howard Dean and DSCC Chairman Chuck Schumer hopefully know that they can strike rare gold in Oklahoma if they just try.
The chief problem is getting a candidate. As neither Boren nor Henry seems remotely interested, the Democrats will probably have to run a fairly unknown candidate. That will make it unfortunately easy for Inhofe's campaign to paint the Democratic candidate as extremely liberal as was done to Tester in Montana (and it nearly saved Burns, who should have lost reelection badly even if he were from Utah).
Can the Democrats overcome that? I'm not sure.