By Alec MacGillis BEND, Ore. — After all the bowling and the shot-and-a-beer quaffing of the recent Rust Belt primaries, the upcoming Oregon contest is serving as a useful reminder of a fact that's been somewhat overlooked: not every swing voter in America wears a blue collar. Hillary Clinton's campaign has been arguing for several months that her strength with white working class Democrats would make her better positioned to win key states like Pennsylvania, Ohio and Michigan in November. And there is no doubt that Barack Obama has work to do in winning over this group of voters, though his campaign argues that many of them voters will remain in the Democratic fold come November. But the fixation on Rust Belt Reagan Democrats has given short shrift to another, and by some measures more numerous and pivotal, group of swing voters: middle and upper-middle income independents who jump from