In a two party system, populist movements grow when the opposition party is failing (or is perceived as failing) people. Alternatively, both parties can fail the people before one becomes populist.
The two party system has failed Americans. But now that the republicans have created a populist movement, the failure of democrats to properly serve many people causes them to be pulled by populism. It doesn’t help that the culture war lets absolue horseshit issues fly by without actual basis in reality, since that fuels the fire without actually having to do the hard discussions about policy.
The MAGA movement is a “third way” that formed because the paths forward shown by both democrats and republicans seemed to lead to nowhere for many people.
I don’t think this is a cancer, I think this is a horrendous feature of the design of a representative democracy under capitalism (at least, in the American sense)
Capitalism will crush people while trying to wring every bit of profit out of them, and in a capitalist democracy, the state supports capitalism.
Representative democracy leads to unaccountable representatives. They still need to get re-elected if they want to (or they could just serve capital and dip), but with all the dogmatism caused by political parties, the hierarchy of the parties protecting the politician, and the benefits of having corporate sugar daddies, especially media corporations, they can get away with enriching themselves at the expense of Americans, while still having decent odds at reelection.
Further, people in power, for whatever reason gave this tendency to build their power, usually at the expense of those without it. The state gives itself new powers and new toys at the expense of everyone else. Fear of terrorism gave us some of the most draconian laws on the books, such as the patriot act, which has not been repealed whenever there has been an opportunity to. The police got afraid of the people, and bought themselves guns, counterinsurgency training and tools from a foreign apartheid state, armored cars, and raises. The supreme court went from writing itself into existence to giving the president near legal immunity, rolling out the red carpet for the authoritarian state to become an even more authoritarian state.
When you mix these tendencies together, its no wonder why this state has failed. And while it hasn’t failed everyone, the nature of capitalism leads to a pretty large exploited class ripe for exploitation. And this populist movement is ready to take advantage of that, between those primed by culture war drivel, economic suffering, or seeing their demographic and/or class lose power in some way.
This populism isn’t a cancer on an ailing democracy.
It is a symptom of a failing democracy, unable to sustain itself from the structure of itself.