Some people seem to enjoy national politics as a kind of spectator sport with audience participation.
They vote in the general election for the team they support. They vote in the primary election for the candidate who will best help their team win in the general election.
They reject the option of voting for a superior candidate on the other team, or for a candidate not on either team, because this might tip the balance for the other team.
When I point to the bipartisan acceptance of the USA’s drift into financial oligarchy, economic stagnation, authoritarianism and perpetual war, the answer I get is that one party is worse than the other, and that is the only relevant consideration.
As committed political sports fans, they made an initial decision as to which team to support, and any subsequent decision is based on its implications for their team’s victory or defeat.