Seriously, one look at the Republican party should tell you this. Republicans are an alliance of convenience of four major groups, none of whom share much common ground beyond their hatred of the Democrats:
-Big Business and the Wealthy, who are in favour of deregulation and low taxes, but otherwise generally favour socially progressive policies (because then the government is paying for things that they would otherwise need to provide for and/or which, if left unaddressed, would impede their ability to accumulate wealth - think healthcare or education).
-The Religious Right, who generally favour socially conservative policies on religion and abortion, but often still favour a strong social safety net for moral reasons.
-"Tea Party"-style far-right - mostly wonks who favour extreme positions on low taxes, privatization of everything, and the removal of as much of the government as possible.
-The MAGA Cult, whose beliefs are whatever Donald Trump says they are at the time. The most fascistic of the group, they favour a large, centralized government (directed at outgroups they don't like), which is against traditional conservative orthodoxy, but they're currently a large enough faction to overrule the old guard. Generally more focused on identity and grievance politics, as well as fighting the culture war, than the other three groups.
These four groups share an uneasy alliance, but one look at Republicans trying to govern (or the slew of Republican voters asking what the fuck Trump is doing right now) should give you some idea as to their (lack of) unity of purpose, as many of their goals are mutually exclusive, if not outright antithetical to one another.
Democrats are more united, because groups further left tend to have a greater appreciation of the needs of the collective than groups on the right, but they also have a larger proportion of "soft"/apathetic voters who don't turn up for them.
Well said.
To this I would like to add a 5th faction, split off from Big Business: News and Social Media.
Id argue their interests are not the same as Big Business: they want to manufacture chaos, discord, unrest, all to farm clicks. Unlike GE or Xerox or whoever, they don't actually provide a service anymore. Their main goal is shaping cultural narratives and then scamming on the side.