A sense of history is required to fully appreciate the impact of Keith Parker's decision to leave the helm of MARTA.

Just seven years ago, the relationship between the Georgia’s premier transit agency and the state Capitol was as cozy as a knife fight on a dark waterfront.

Republicans in the Legislature, the keys to state government still fresh in their hands, couldn’t decide whether MARTA was a criminal operation, an ideological threat, or merely rife with incompetence.

State Rep. Jill Chambers, then chairman of the legislative oversight committee for MARTA, had waded so deeply into its finances that the transit system ponied up an extra $480,000 for Capitol lobbyists – just to keep up with her demands for this file and that.

There was some substance to the suspicion. MARTA’s finances were indeed a mess, and insolvency was on the horizon -- although handcuffs the Legislature had put on how the transit agency could spend its primary source of funding, a penny sales tax, was part of the problem.

Hostilities were mutual. When the state refused to help offset a $120 million funding gap in operations, CEO Beverly Scott had giant red X's painted on the sides of one third of MARTA's buses and had them circle the Capitol.

Scott fled to Boston two years later, whereupon the next chairman of the MARTA oversight committee felt it proper to flex his muscles. State Rep. Mike Jacobs of Brookhaven all but named his candidate. The right appointment, he said, "could go a long way to shoring up and bolstering the relationship with the General Assembly."

Instead, the MARTA board hired the president and CEO of the bus system in San Antonio. Thus, the Keith Parker era began as an act of defiance. And succeeded admirably.

Five years later, even as he leaves, Parker is a celebrated figure in the state Capitol. While he may not be the sole reason, he is often the first one Republicans cite when describing their changed attitude toward commuter rail in metro Atlanta.

One measure of the improved diplomatic relations: Parker made his decision to leave to become president and CEO of Goodwill of North Georgia last week.

That Wednesday, eight days ago, MARTA board chairman Robbie Ashe began making quiet phone calls to all stakeholders, informing them of the development. Not just to the traditional Democratic recipients such as Atlanta Mayor Kasim Reed and DeKalb County CEO Michael Thurmond, but to a raft of Republicans in the state Capitol. The governor, the House speaker, the lieutenant governor, transportation committee chairs.

The most interesting name on that contact list belonged to House Speaker pro tem Jan Jones, R-Milton. Any renewed push to run a rail line over the Chattahoochee River in north Fulton won’t be done without her say-so.

Another measure of thawed attitudes: Figures in the Capitol sat on the Parker secret for five days, an almost unheard-of act of discretion. And, perhaps, respect.

The question now is whether Republicans have been in the thrall of a Parker personality cult, or is the GOP attitude toward big-city investments truly changing.

”I think MARTA’s on a good footing now. I don’t think it’s going to fall apart because one person leaves,” said state Rep. Tom Taylor, the current chair of the Legislature’s MARTA oversight committee.

The most important figure in Georgia transportation right now may be state Rep. Kevin Tanner, R-Dawsonville. He chairs the House commission that’s now looking at whether – and if so, how – state government should fund transit.

Since starting out this spring, Tanner’s commission on transit governance has already met once at MARTA headquarters, another unprecedented act of diplomacy. The group’s next meeting is Sept. 15 in Gwinnett County, an act of chutzpah that would have brought out the local pitchforks only a few years ago.

Tanner termed Parker’s departure as “unfortunate,” but said MARTA’s turnaround has been a group effort. “I think it’s the tone that the MARTA board has set, from the chairman on down,” he said. ”Robbie has done a good job. I think they see the need for all of us to be working together for a common cause.”

Brandon Beach, R-Alpharetta, chairman of the Senate Transportation Committee, first confronted metro Atlanta’s traffic problems as a member of the state transportation board. More recently, he has been the primary packhorse for MARTA legislation in the Capitol.

Beach will grant you that Parker improved the ridership experience at MARTA. He upped police presence and cut down on “knucklehead” behavior on trains. He introduced wi-fi. And vegetables at certain stations.

But like Tanner, Beach points to the breaking down of metro Atlanta’s feudal barriers as the real change that Parker helped lead.

“Twelve years ago, when I first got on GDOT, I can tell you that GDOT didn’t talk to MARTA, and MARTA didn’t talk to ARC, and ARC didn’t talk to GRTA, GRTA didn’t talk to GDOT. They were all silos of organization,” Beach said. “There was no collaboration or communication. And that has changed.”

The ruling members of metro Atlanta’s transportation bureaucracy now gather for regular coffee klatches: Parker as the head of MARTA; Chris Tomlinson, executive director of the State Road and Tollway Authority and the Georgia Regional Transit Authority; Douglas Hooker, leader of the Atlanta Regional Commission, the overarching planning agency; and Russell McMurry, the commissioner of the state Department of Transportation.

The gatherings have already paid off: The night of the I-85 fire last spring, before the flames were out, MARTA and GRTA were on the phone with GDOT, rerouting and rescheduling services.

Neither Beach nor any other state legislator we contacted thought MARTA would have trouble finding a replacement for Parker. The improved political climate is one big reason. A huge project on the horizon – the expansion of rail service to Emory University and the U.S. Centers for Disease Control and Prevention is another.

And face it – the transit business is far more attractive in times of economic plenty. Beach points to the dozen or so giant construction cranes scattered throughout Midtown alone.

But if you want one last bit of proof of the improved state of transportation politics in metro Atlanta brought about by Parker & Co., there’s this: I asked Beach if he wanted any say over who becomes the next general manager and CEO of MARTA.

“No,” he said. “That’s the MARTA board’s decision.”