Updated at 8:30 p.m.: Regardless of what happens in the Legislature, we're about to find out what north Fulton County, and a good portion of neighboring Cherokee County, think about extending MARTA rail their way.

On the first day of qualifying for the May 24 primaries, state Sen. Brandon Beach, R-Alpharetta, author of the MARTA rail bill, has picked up a GOP challenger.

Aaron Barlow, 41, is veteran executive with Equifax, Arthur Andersen, and TransUnion who has left the private sector in favor of philanthropy and, at least for the next 77 days, a self-funded candidate for state senator.

Watch who lines up behind whom on this one. It could say much about where transit is headed in metro Atlanta. We’ve reached out to Beach and hope to hear from him quickly.

Outside the Republican encampment in the Capitol, Barlow said he is a supporter of “religious liberty” legislation aimed at protecting wedding photographers, bakers and such whom he says could be forced into catering same-sex nuptials. Said Barlow:

"I feel like we are too quick to assume the worst about laws that are already on the books in 32 states and the federal government, and really aren't materially different from that."

But Beach voted for HB 757, the working version of a religious liberty bill, which has been sent back to the House. So there's not much difference there.

No, the big issue in the District 21 race will be SB 330, Beach's bill that would let voters decide whether to give the transit agency a half-percent sales tax over several decades to pay for a massive extension of rail into north Fulton, east into DeKalb, and elsewhere.

With SB 330 mired, MARTA is talking about a smaller version of the bill, but Atlanta Mayor Kasim Reed says he's not ready to give up on the big lift. Either way, Barlow said the effort will be the focal point of his campaign. Said the new candidate:

"I do lots of deals in the private sector, and something at a high level can sound attractive, but when you get into the details you discover this just isn't worth it. So in Fulton County, for instance, it's troubling for those folks. We've polled the district and found this is the case.

"If two-thirds of the money is going to be raised in Fulton County, but redound to DeKalb, that's a problem. If the tax is going to last 40 to 50 years, that's a problem. Half of us will be dead by the time the tax ends.

"If it takes 20 years to build the system, and we don't have it until then – the same chamber of commerce that is advocating for this sort of solution also has on its website a wonderful discussion of the advances being made in car technology. We already have driverless cars. In the next 20 years, I wouldn't be surprised if the automobile makers don't end up making those investments for us. To some level – I'm not saying it's a panacea. But that's free. That doesn't cost us $8 billion."

Barlow brought up the name of the Republican incumbent only once:

"This is county welfare. Fulton County is subsidizing DeKalb County under Brandon Beach's bill. And that's county welfare. If DeKalb really wants it that badly, they should pay for it."

Updated material: If you read this article earlier today, you'll note that we quoted Barlow as accusing Beach's bill as helping Cobb County. After we posted, Barlow called to say that he had said "DeKalb" -- pronouncing it "De-Kobb."  Checking the audio, we take his point.

We have also heard from Senator Beach, who said he looked forward to presenting his conservative credentials to the voters of his district, noting that his MARTA legislation presented them only with the opportunity to vote on the matter. Beach also noticed his more local accomplishments, including a new technical college for his district.