Political scientist Seth Masket has this relatively short and simple summary of political science research showing that type of primary does not effect whether moderates or extremists get elected. The article is in Pacific Standard, an award-winning bimonthly magazine that has existed since 2008. It is published in Santa Barbara, California. Thanks to Rick Hasen for the link.
NO primaries — which only produce EXTREMIST robot party hacks from Hell — who later get elected in totally rigged gerrymander areas — States, Districts.
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P.R. and nonpartisan App.V.