1) The candidate who lost the previous match can give the sore loser image vibes off.
2) The candidate can fail give voters a reason to vote for him this time.
This is why I do not think Applegate is necessarily a shoo-in to defeat Issa in 2018. Even if the circumstances will be possible.
I personally experienced this first hand when it was obvious that Doug Owens was giving a sore loser vibe and failed to give voters a reason to vote for him and boot Love. He could not really disqualify Love.
Strange things have happened in American Politics but I think Love could be quite secure even if Trump is very unpopular among Mormons as she never really embraced Trump at all. However her support still is stuck in the low 50s.
This article makes me sad: https://www.ksl.com/?sid=32236467
To be fair, other than Owens, we only have about 2 or 3 other credible candidates, assuming no state legislators or County Council/DA types run.
Now that he's lost twice, he's no longer a credible candidate, and lobbyist Matheson is unlikely to run. Ben McAdams could run, but he seems content to be County Mayor, and maybe try for Governor in 2020.