Table S1.

Balance check across demographics

Treatment group	% Female	% Democrat	% African American	2008 primary turnout	2006 general turnout	Average age*
Control	59.78%	55.14%	15.28%	32.04%	80.66%	43.34
(n = 76,963)	46,008	42,437	11,760	24,659	62,078	76,498
Nonobservable	59.67%	55.02%	15.59%	31.96%	80.69%	43.24
(n = 346,929)	207,013	190,880	54,086	110,879	279,937	344,874
Observable	59.72%	55.09%	15.55%	32.10%	80.69%	43.29
(n = 347,054)	207,261	191,192	53,967	111,404	280,038	344,899

Multinomial logistic regression: LR chi2(12) = 8.96, P = 0.7063.

^*Age was missing for a small percentage of the observations.