The other thing that emerges out of this system is that people who do want to influence elections ideologically primarily do it by organizing or funding interest groups outside the party structure (though often tied to interests within it), and only secondarily within the party structures.
They then attempt to mobilize people to share/who share their views in “get out the vote” efforts, which, if successful, have the effect of shifting the ideology of the actual electorate (if more people who believe x vote, the “50” moves in that direction).
The other thing activism does is shape the perception politicians have of where that “50” is (letter-writing campaigns, protests, and other schemes to make a group seem numerous or at least intensely interested – and voter intensity often matters, out of the numbers involved. Intensely interested minorities can often get their way on issues of interest to them, because it matters more to them than to the average voter).
Then there’s the ultimate way of shifting the electorate, which is not directly done by parties at all: managing “public opinion” (Chomsky often highlights the concept of “manufacturing consent,” and Lippmann, but without noting that at the time Lipmann wrote that, Walter was a left-progressive social democrat. This is their method, though now it’s also attempted, with less success, by the right), capturing institutions that promulgate ideas and other methods of, to put it starkly, mind control/manipulation methods.
This is one reason why education, both “higher” and “primary,” has become corrupted. It’s the ultimate way to sway electorates by inputting beliefs directly into impressionable young people.