My new TRB column explores the different ways the two parties operate. Democrats try to maximize the number of seats they hold, while Republicans try to maximize the discipline of their caucus.

In return for imbuing their members of Congress with fanatical discipline, Republicans have a lot fewer of them than they could. Here’s one way to look at it. The House is naturally tilted toward the GOP. Democrats have more heavily packed urban districts with overwhelming majorities where their votes are wasted. The median House district is 2 percentage points more Republican than the country as a whole. The Senate is even more Republican-tilted, with Democrats clustered in underrepresented large states. As political scientist John D. Griffin found, “[I]ndividuals residing in states with less voting weight are quite consistently more liberal and more likely to identify with the Democratic Party.” Of the 60 Senate seats Democrats briefly controlled in 2009–2010, 22 of them represented states that had voted Republican in at least two of the three previous elections. Just four Republicans senators represented states that had voted Democratic in at least two of the last three presidential elections.
Republicans, whether consciously or accidentally, have “spent” their structural advantage in Congress on demanding near-absolute party-line discipline. Democrats have controlled far more seats than they ought to—in 2000, with the parties at parity, Bush won 30 states, but Republicans haven’t come close to holding the 60 Senate seats that ought to be their natural baseline.

The column doesn't really strike a judgment as to which method is better. If I were running a party, I'd try to impose more partisan discipline than the Democrats have but less than the Republicans have. Anyway, the column is subscriber-only, so do subscribe if you don't already.