For example, the 2016, 2020, and the pseudo- 2024 Democrat Primaries have shared a significant crowd. People have come and gone(Bernie gave up in 2024. Biden didn’t stick in 2016 long due to family issues), but for the most part you’ll see the same people. Or the Republicans from 2008-2012, mostly the same guys. Heck, Hillary and Biden, the future nominees, both did really well in 2008, coming second and 3rd(ish) overall. Al Gore had tried prior to Bill getting in. Even way way back you had guys like Henry Clay trying and trying and trying.

But then you compare something like 2012 Republican Primaries to the 2016 Republican Primaries. None of the big names return, no Mitt Romney, no McCain, no Newt Gingrinch, no Rick Sanctorum, no Ron Paul, no Fred Karger. The ONLY returnee at all out of like 15-20 serious contenders was Rick Perry, who was a minor nominee that dropped out early both times. The big 5 or big 6 or even big 7 were completely different.