Most embarrassing campaign by election

[I spent the winter writing songs about getting better]

Here's my picks:

2024: So far, obviously Ron DeSantis.

2020: If asked at the point Biden secured the nomination I'd say Kamala Harris, but she ended up getting the VP spot out of it so in the end not really. Michael Bloomberg thus becomes the obvious answer with how much he spent per delegate. Actually one could argue he even tops Harris for that reason.

2016 R: Jeb. Pretty easy.
2016 D: With the general election obviously Hillary. But in just primary season....either Martin O'Malley or Lincoln Chafee, the latter had dirt low expectations and still managed to fail to meet them. O'Malley actually had some level of hype though so...

2012: Rick Perry, if nothing else for that debate moment. Even with it he was kind of the biggest underperformer.

2008 R: Rudy Giuliani. The standard bearer pre-Jeb.
2008 D: Technically John Edwards but not really fair to base this on a scandal that broke after his campaign. I'll say Bill Richardson for being somewhat hyped and going nowhere ala Martin O'Malley.

2004: It feels kind of weird saying this because he had a pretty notable rise to begin with and still managed to make a good career out of it...but Howard Dean definitely is a possibility with his performance once the primaries actually started. But the "winner" here has to be Joe Lieberman.

Not sure about 2000 and prior.