But in the US the voter does not expect to vote for a party, they expect to vote for a person. Their party affiliation is an important attribute, but not the only one. For an incumbent in a general election the voting record and constituent service is more important than the party. An incumbent who played the part of the loyal opposition voting against all major initiatives of the majority would not last except in the most solid partisan districts. In a 55-45 district that just won't do.
Coming from you, muon2, I trust that this is true, and it does make me feel better about things. Even a cursory think would lead one to the conclusion, I suppose, to assume that, in districts with margins of 10 or less, there would be enough swing votes to cost a rep. their seat if they themselves were overly partisan and did not deliver for their constituents. In fact, I remember even when growing up in North Dakota, when one of our U.S. Senators Quintin Burdick ran for reelection, his campaign ads were all about his "clout" and seniority, and how little sense it would make to send a newbie to Congress who was in a worse position to bring home goodies for the state; he never mentioned his party affiliation.
On the other hand, at least since the mid-'90's in Congressional elections on the national level, campaigns have become "nationalized" and party machinery on both sides of the aisle have, it seems to me, tried hard to polarize the voters along partisan lines, with some success.
