Qualifying for the 2016 elections opened Monday, and the first day of the weeklong process found 13 incumbent Georgia state lawmakers and four federal officials land primary opponents.

All 236 state legislative seats, 14 spots in the U.S. House, one U.S. Senate seat and one Public Service Commission post are all up for grabs. Candidates have until noon Friday to qualify for the May 24 primary.

Among the most interesting developments of the first day of qualifying came from investor Aaron Barlow of Milton, who will run against incumbent state Sen. Brandon Beach, R-Alpharetta. Beach has been a leading advocate for expanding MARTA into the northern suburbs. Barlow opposes Beach's plan.

“MARTA is the big one for sure,” he said. “My concern is not necessarily with the idea of public transportation. Public transportation is a fine concept. It’s just that the cost benefit needs to be there.”

Efforts to reach Beach were unsuccessful.

In North Georgia, retired wrestling coach Sam Snider will once again challenge House Speaker David Ralston, R-Blue Ridge, despite getting only 35 percent of the vote in their 2014 matchup.

Snider, in a statement announcing his campaign, said the 2015 transportation bill that increased state gasoline taxes and the Legislature’s failure to pass a “religious liberty” bill convinced him he should run again.

Ralston said Monday that he is proud of his record and that his challenger should articulate what he’s for, not just what he’s against.

“The citizens of our area deserve as much,” Ralston said. “Dark money and shady political operatives flooded my district in the last election spewing negativity, and their selfish agenda was overwhelmingly rejected. I will again trust the good judgment of the people of House District 7.”

On the federal front, political newcomer James Knox signed up as a Democrat to run against incumbent Republican U.S. Sen. Johnny Isakson. Democrats have long sought a credible challenger to Isakson. Knox, a retired Air Force veteran, features a quote from Ronald Reagan on his campaign website. At least one other Democrat is expected to enter the race.

Isakson also faces a primary opponent: Derrick Grayson, who also ran for the Republican Senate nomination in 2014. The Federal Election Commission "terminated" his campaign account in November for failure to file campaign finance reports. Libertarian candidate Allen Buckley is also running.

Republican U.S. Reps. Rick Allen, Doug Collins and Barry Loudermilk also face primary opponents. Allen will face Eugene Yu. Roger Fitzpatrick is challenging Collins, and Hayden Collins will run against Loudermilk.

Several former lawmakers are seeking a return to the state Capitol. Delvis Dutton, a former House member who ran unsuccessfully for Congress in 2014, qualified to run for the state Senate seat held by Tommie Williams, R-Lyons. Williams is retiring. Dutton will face Toombs County Commission Chairman Blake Tillery in May.

Lee Anderson of Grovetown, also a former House member, qualified for the open Republican primary in Senate District 24, now held by the retiring Bill Jackson, R-Appling. Business owner Gregory Grzybowski has also qualified.

On the Democratic side, the decisions of two young up-and-coming House members not to seek re-election created two open Atlanta-area seats. State Reps. LaDawn Jones, D-Atlanta, and Ronnie Mabra, R-Fayetteville, have said they will not run again.

Four candidates qualified for Mabra’s seat on Monday. Several are expected to run for Jones’ seat, too, although only attorney Valerie Vie registered Monday.

Longtime state Rep. Roger Bruce, D-Atlanta, said Jones and Mabra had bright futures in the party.

“Both of them were part of the next generation of legislators,” Bruce said. “But this is not a job you can earn a living at, and both of them are aspiring lawyers and both have new families.”

Bruce said he’s hopeful that Democrats can gain momentum and win back a seat or two from Republicans. The party has targeted several swing districts. Bruce said this as he noted the long, snaking line of Republicans waiting to qualify, compared with the relative calm of Democratic sign-ups.

“I look at the number of people qualifying on that (GOP) side compared to this side,” Bruce said. “When I see that many, it means some of those incumbents might not be coming back.”

Seats where the Republican incumbent is defeated in a primary could be easier to win in November, he said.

But state Rep. Dominic LaRiccia, R-Douglas, said that might not be true this year. Conservative voters are motivated.

“I don’t think it’s anti-incumbency as much as it’s just frustration of the people,” he said.

LaRiccia, a freshman legislator, said he’s still not sure whether he’ll run again.

“I really want to be patient,” he said.