For only $250? Money goes much further in WVA? :)
It's not a bribe; it's a symbolic overture. I doubt Manchin (& Earl Ray, et al) care primarily about ideology - it's about power. So if the Republicans take control of the Senate, he would like to be in the majority. It's easy for him now since Harry Reid doesn't let the Senate vote on anything and he can talk conservative all day long for the folks back home. But with a closely divided Senate under a GOP majority, Manchin would have to take stands on tough issues again and again and he doesn't have the stomach for it.
As a Republican, Manchin would probably line up with the leadership most of the time, more than a Collins/Brown type. Maybe like Ben Nighthorse Campbell.
WV has two GOP Congresscritters now and votes GOP in presidential races. They can read the writing on the wall. It's just a matter of when.