No large political party has shown intention of electoral reform, and no large party ever will. The Liberals betrayed electoral reform. The BC NDP has abandoned efforts for PR. The Alberta NDP isn't going to do shit.
This is purely because electoral reform doesn't benefit large parties in a given election race.
So here's just a quick idea. What if a single issue group is made, that's independent of party lines with a single affirmation:
"I am person X, and I'm a member of party Y. I will not vote in the upcoming election unless my party promises to enact MMPR within 365 days of forming government. If they betray this promise, I will not vote in any given election until electoral reform is passed".
While I don't have data, I think that people irrespective of parties, AND non leading factions within political parties would like PR. Why?
People: Most people I've encountered, hate what their party does. The only way they vote is to keep the "worse guy" out. I've observed this in the Federal liberals, Alberta and BC NDPs and even the Alberta UCP. If we frame this correctly as "people vs politicians" instead of "party A vs party B", then there could be some non partisan momentum to this.
Politicians: As a politician in the current system, either you join the two largest political parties in a race, or you never win a seat. The Alberta NDP for example, is made up of quite a few politicians who ideally should've been Liberals or Greens. Same with the UCP, who should've been everything from Liberals, progressive conservatives to straight up separatists.
Splitting up into independent parties without fear of vote splitting gives more power to these politicians as well. I can't see why a politician would be against gaining more power.
Also, the movement doesn't even have to be THAT large to be a pain in the ass for political parties. Seats are won on razor thin margins. If even a single digit percentage of the electorate identifies as the "MMPR or we won't vote at all" bloc, then political parties are forced to address these demands if they have any desire to win.
It would need a lot of organizing and campaigning. The main action wouldn't be withholding the vote but the organizing behind a cohesive message. You (as a collective) would have to agree on what exactly are your demands and be loud about it.
I agree that lesser evilism will only ever lead to more and more evil candidates as long as the other candidate is more evil, but reversing that course is going to be tough.