The worst-kept secret in Tennessee politics appears to be on the verge of being spilled.

Randy Boyd's resignation Monday as the state's commissioner of the Department of Economic & Community Development comes as he is widely thought to be gearing up for a gubernatorial run next year.

The Nashville Post reported Monday that Boyd "is resigning from his post — likely to prepare for a 2018 gubernatorial run."

Actually, that statement may not be altogether accurate. Boyd's appointment as ECD commissioner was likely, in itself, preparation for a gubernatorial run.

It could be, of course, that Boyd is simply ready to return to the private sector. He is a multimillionaire businessman, owner of the company that makes the PetSafe brand of invisible fencing for dogs and cats, among other products, and also owns the Tennessee Smokies and Johnson City Cardinals minor-league baseball teams.

It could also be that Boyd needs more time to focus on what some think might be his next big project: moving the Smokies from Kodak to a new stadium in downtown Knoxville.

But the prospects of Boyd seeking to replace his friend Bill Haslam in the governor's mansion have long been the source of speculation in Nashville and beyond. Employees of ECD and other state departments have whispered about it for years.

State Sen. Mark Green, R-Clarksville, announced last week that he will seek the GOP's gubernatorial nomination, formally confirming what had been unofficially certain for months, and there will likely be plenty of other Republicans who follow suit.

That makes it important that Boyd get an early start to his campaign. And Green signing on with GOP strategist Darren Morris makes it even more important still. The Morris name won't ring a bell for many, but he was chief of staff for Donald Trump's Florida campaign, and also directed Trump's primary campaign in Tennessee.

In seeking the governor's mansion, Boyd will attempt to take a path similar to that of Haslam: that is, a successful businessman who seeks the gubernatorial office as a relative newcomer to politics. While Haslam left the family's Pilot brand to cut his political teeth as Knoxville's mayor, it could be argued that Boyd has gained equal experience — and perhaps name recognition — through heading up ECD.

It's hardly a given that Republicans will hold on to the governor's mansion again in 2018. Tennessee is a deeper shade of red now than at any point in its history, but Democrats are lining up some potential candidates who will prove formidible. Among them, Karl Dean may be set to attempt to follow in Phil Bredesen's footsteps as a well-liked former mayor of Nashville who seeks the gubernatorial office as a Democrat.