Fincher, who helped craft a "school choice" bill in the state, joins columnist and conservative activist Quin Hillyer (R), state Rep. Randy Davis (R), businessman Dean Young (R), former Marine James Halland (R), realtor Jessica James (R) and former state senator Bradley Byrne (R) in the primary race.
Bonner is leaving Congress in August for a job at the University of Alabama.
Hillyer, meanwhile, became the first candidate to release an ad for the race. Hillyer has more national political connections than the other candidates, and some outside groups have already endorsed him.
"Time after time, Obama's government has betrayed our trust," the ad's narrator says. "It's time to fight back. It's time to send a strong conservative Republican to Congress. It's Hillyer time. Quin Hillyer: bringing Alabama values to where they're needed the most — Washington."
Whoever wins the crowded primary will be the heavy favorite in a district Mitt Romney won with 61 percent of the vote.