Manchin just barely won the last time because of two reasons.
1. Manchin played the “You’re Not a Native Son!” card hard! That still matters In WV particularly to older WV’ians. Though every election it matters less! Manchin had no senatorial accomplishments to run on! The “You’re not from around here are ya?” card was all he had!
2. Relatively ineffective campaign run by the GOP candidate.
I’ll add (3) The Democrats supported a Libertarian as a sort of stalking horse, for the YAFAH folks who can’t stand Manchin.