they just don’t succeed frequently enough for it to be called fair
Statistically speaking, the majority of campaigns are going to fail. There’s one seat and, unless it is uncontested, a minimum of one losing candidate. But politics isn’t a one-and-done game. Its a game of coalition building and expanding name recognition. Starting off as a third party candidate, establishing a message and a political brand, and then canvasing your neighborhood to build up your appeal is fundamental to most successful politicians.
But because of the spoiler effect
The spoiler effect only matters to losers. If you’re the guy with the plurality of support, you’re in the best position to win.
Sometimes, the winning move is simply to carry the banner of the dominant political party (which is why you’ll have a dozen people compete for the Texas GOP gubernatorial nomination while only two or three bother trying to run as Dems). But other times, it really is about issues-based politics and name recognition.
Schwarzenegger was able to win in California by being a famous popular guy. Sanders won in Vermont by being a high profile well-respected mayor of the state’s biggest city. Joe Lieberman lost his primary but held onto his Senatorial seat back in 2006 by rallying the Democratic Party leadership around him even after he’d lost the state party nomination.
Bush beat Gore in 2000 not because of a Green Party spoiler effect (Nader actually pulled more Republicans than Democrats in the state) but because he had die-hard conservative activists willing to risk jail to shut down the recount with the Brooks Brothers’ Riot, while Al Gore’s party just kinda shrugged and gave up as soon as the Republican-leaning SCOTUS sided with the Republican candidate. Hell, the 2000s were awash with caging, disenfranchisement, gerrymandering, and outright election stealing from the top of the ballot to the bottom. Third parties didn’t have anything to do with that.