"The premise behind the spectacle is that candidates win by competing for those not sure of whether they are for or against civil rights, tax cuts for the rich, and so on. Yet much evidence suggests that political organizations benefit most from motivating those who already agree with them, and that the Democrats in particular find the most success by pursuing people who don't know whether they'll vote, rather than how they'll vote. This means reaching constituents who, historically, have been less likely to go to the polling booth: the poor, the young, the non-white. Republicans know this, which is why they've worked hard to perfect voter suppression tactics that target those populations.
"Nevertheless, centrist Democrats often go wooing those who don't support them, thereby betraying those who do. It's as though you ditched not only your congregation but your credo in the hope of making inroads among believers of some other faith. You think you're recruiting; really, you're losing your religion. This has been true with welfare 'reform,' with the war on terror, with economic policy, with the fantasy of winning over 'the white working class': time and again, misguided attempts to bring in new voters have offended existing constituencies."
-- Rebecca Solnit, "Preaching to The Choir", Harper's Magazine, November 2017