My reasoning is simple.
The pattern may turn out to be Conservative candidates running against the GOP and primary candidates challenging Democrats.
If the fights in both parties tend this way, the Democrats win hands down. Almost no third party candidate wins. The sad exception last time was Lieberman who got defeated in the Democratic primary.
I believe the electoral dissent will boil over on the Republican side and result in third party runs by defeated GOP primary candidates. If Democrats avoid this pattern they have a lock both Senate and House.
The disgust with both parties comes from two different perceptions. Progressives are tired of bought and paid for Democrats. And the wingnut shrunken Republicans simply want to destroy the party they are ruining every time they open their mouths.
The best thing is that there is a majority that leans toward the Obama agenda. If that changes we are in deep trouble. We would be where we were when the minor dark age we live in was sealed in 1968.
I believe that fate will pass us by. Dems need to hang tough and keep battles within the party.
Republicans will be unable to. That means their fate is worse than it even is today.