In Australia, mandatory voting is compelled real or virtual attendance.
You are required to cast or mail in an anonymous response, that response can be blank, a vote for someone not listed, a regular vote, a donkey vote, paper with many pictures of various genitalia, etc.
No speech is compelled, no pen to paper is compelled, just that registered voters are ticked off the rolls and those registered that don't respond provide at least a weak excuse (my grandmother was sick that day) or face a nominal fine (eventually).
Think of it a citizens part to play in a democracy, the commitment to at least pay attention to the government hired by and paid for by citizens.
The fine for not voting in Australia is about $30.
This is...nothing in the grand scheme of things.
But it's enough.
And you don't even have to vote: you have to turn up, that's it.
A couple cycles of this will flush the crap out of the system.
Or that my "proposed" solution, in many ways, describes the current status quo. Tricks like California's Prop. 13 have created enormous gaps between the taxes paid by the old and the young. Warren Buffet has criticized how much lower his own (income) tax rates are than his secretary's rates.
Some days I feel really, really old.
Those people would heavily incentivized to protect their ability to vote.