What went wrong for Jimmy Carter in 1980?

[Cyrusman]

It’s not that he lost it’s how bad he lost as an incumbent President.

What the heck happened?

[morgankingsley]

It is important to note that despite the EV, Carter is not actually the biggest defeat for an incumbent. Hoover lost by seventeen, Taft lost by almost twenty, by comparison, Carter lost by "only" nine. There were also seven states decided by less than two percent, which would have accounted for sixty-three electoral votes, and could have easily gone to him had he had a little more luck, or Reagan had a little less luck, or had Anderson simply not run and two third of his vote go to Carter. The point is that while Carter did lose big, it is important to note that the magnitude of his landslide is widely blown out of proportion

[dw93]

It is important to note that despite the EV, Carter is not actually the biggest defeat for an incumbent. Hoover lost by seventeen, Taft lost by almost twenty, by comparison, Carter lost by "only" nine. There were also seven states decided by less than two percent, which would have accounted for sixty-three electoral votes, and could have easily gone to him had he had a little more luck, or Reagan had a little less luck, or had Anderson simply not run and two third of his vote go to Carter. The point is that while Carter did lose big, it is important to note that the magnitude of his landslide is widely blown out of proportion

Also, Carter at least managed 40% of the popular vote, Bush only got 37% in 1992.

[Amenhotep Bakari-Sellers]

He had a divisive primary with Teddy Kennedy; as a result,  turnout among ethnic groups were low. However, Reagan was Irish and was able to capture the Latino vote in CA, NM, and NV, the critical states that were needed to win; that, otherwise, would have went to Kennedy..

If Kennedy won CA, NV and NM, that would have clinched the election for him.