They have enough gerrymandered districts, voter suppression, and a sufficiently mobilized voter base to make up for the rest.
And Democrats arent fulfilling the promises they made to the rest of the voter base. Leading towards another defeat - just like in 2016 - independents, youth, disenfranchised poor not coming out to vote is enough to tip the scales.
https://ozgurzeren.medium.com/with-the-rate-things-are-going-trump-may-come-back-db089f49fb11