We went a long way toward swinging the needle in the House to the left in the 2006 election. Obviously, this is a direct result of picking up 30+ seats, but there's more to it than that. It's also a matter of replacing Republicans with the right people: replacing a right-wing nutter with a progressive goes a much longer way toward than replacing a moderate Republican with a Blue Dog, and we did more of the former. In addition, most of our open seat replacements wound up being more liberal than their predecessors.
To explore this, I matched up the DW-Nominate score* for each representative in each seat in the 109th Congress (2005-2006) vs. the 110th Congress (2007-2008). (I also converted the scores into discrete ranks from most liberal to least liberal, as DW-Nominate scores don't look very meaningful at first glance. However, I'm subtracting the scores, not the ranks, so that we're measuring actual shifts in voting records, rather than measuring distortion caused by an increase in the size of the Democratic caucus.) Let's start by looking at the seats where the overall shift was the largest (not coincidentally, these were the seats that switched from R to D).
