Advocates of a big shake-up in the partisan landscape, whether in the centre or on the right or left, tend to talk about building new political parties from the ground up by fielding candidates in elections. This is vanishingly unlikely to work in the first-past-the-post American system; third-party candidates almost always lack the resources and the name recognition to compete. Voters tend to stick with one of the two major parties in order to avoid the risk of wasting their vote. So upstart parties like the Greens on the left, the Libertarians on the right, or Ross Perot's United We Stand America in the centre face tremendous hurdles, and in practice none have been successful.
A factional split in an existing party reduces that wasted-vote risk. When a faction cleaves from an existing party, it comes with ready-made political power in Congress, and can even play the role of kingmaker. A party that already has members in Congress is a more serious contender in subsequent elections. A strong regional base would probably be needed to stay in contention in any first-past-the-post system; a splinter party that draws 10% of the vote nationwide probably won't win many seats, but a splinter party that draws 10% of the vote concentrated in 25% of the country could.
The biggest weakness in a top-down effort to form a third party via congressional revolt, rather than a bottom-up party-building effort, would be a lack of ideological coherence or connection with voters. A collection of members of Congress disaffected with their leadership will probably not have a strong organic link to any common voter base. But if those members of Congress already come from a common movement with shared organisations and voter bases that had helped elect them, they might take that organisation with them when they split off. Or national political organisations and movements that wanted to form a third party might themselves be the ones pressuring sitting members of Congress to form a breakaway faction.
He doesn't think this is very likely right now, but events might make this more likely to occur:
Of course, there's not much incentive for tea-party Republicans to leave the party right now, since they've succeeded in bending it to their will. But if moderate Republicans finally revolt and dump their agenda, I think tea-party Republicans would have a better shot at launching a sustainable third party than we've seen in America in a long time. Not that it would be a particularly good shot; the segregationist Dixiecrats had a similar combination of congressional power, loyal voter blocs and a unifying ideology when they tried to set up the States' Rights Democratic Party in 1948, and it didn't last past that one election. Still, for anyone who does want to see American politics shaken up through the entrance of a third party, it's worth thinking about the congressional-revolt strategy in combination with the bottom-up one.
