Why is Strange so vulnerable? Usually incumbents - even appointed ones - aren't in that much trouble. He loyally supported Trump in a state that one of the most pro-Trump ones.
1. Appointed by former Gov Bentley, who resigned in disgrace a few months later
2. Appointed by Gov Bentley while he was Attorney General -- while he was supposed to be investigating Bentley
3. Told the Alabama House to stop investigating Bentley for a bit so he could be confirmed (iirc)
4. Heavily funded by Mitch McConnell, who is less popular than cockroaches
Strange fits the 'Washington establishment' stereotype to a T and so Moore -- who is more anti-establishment than John Peter Altgeld -- has taken up the 'drain the swamp' pledge. Trump's endorsement hasn't swayed a lot of people in a local race with lots of complicated factors already involved.