In this dialogue with Matt Miller, Ezra Klein channels a lot of political science to poke holes in Miller’s case for a third party.  Via Facebook, a political scientist friend adds this:

Here’s a question for the third-party types: Why a third party, instead of capturing one of the two? Most third party boosters tend to agree with a lot of what the Democrats want, but not everything. Why not move the party in their direction, from the inside?

In the 1940s/1950s, the Democratic Party wanted what most liberals at the time wanted, but they differed on some issues, most notably on race. Democrats were against civil rights, liberals were for it. But liberals worked WITHIN the party to change its direction, and they succeeded. And that change eventually worked its way through the entire party, from the presidency down through congress and the states. Why is that not the strategy, instead of the incredibly difficult “create a party from scratch” approach?