Argues much of political polarization is driven by the choice set of political candidates

Very multi-pronged argument

(1) Rates ideology of candidates based on the sources of their donations. Show candidate pool is more ideologically divided than before. If in simulation most moderate available candidates always won polarization would still have increased by 80%

(2) Claims moderates would win if they did run. Uses close primaries to show that moderates tend to have an (large?) advantage over the more extreme candidate

(3) Claims that changes in fund-raising, inflation adjusted salaries, and power of congress makes it less appealing for candidates to run

Claim is that by mitigating the factors in (3) politics will become more 'moderate'