Dead body "homosexual" pedophile. That is what it would take.
A necrophiliac.
I don't know of anything Lewis has done to be vulnerable, or even slightly vexed. So far as I can tell, the seat is being described as competitive because of his opponent's resume: Mike Weaver is a retired Army colonel who served two tours in Vietnam. Moreover, he's reported raising $100,000 after just one month of entering the race, which is at least noteworthy.
But the district seems so firmly GOP, as you noted, that I don't even get why a serious challenger would bother, much less why Lewis might actually lose.
PS. And Mike Weaver's also a state rep. for what little that's worth.