TALLAHASSEE — Florida Agriculture Commissioner Adam Putnam filed papers Monday to run for governor in 2018, making official a campaign that has long been expected."I consider myself one of the luckiest people in the world because I get to call Florida home," Putnam, 42, said in a statement. "It's our responsibility as Floridians to keep our economy at work, to increase access to high-quality education, to fiercely protect our personal freedoms, to keep our state safe, and to welcome our veterans home with open arms."Putnam, a former congressman and state legislator, is likely to face a Republican primary challenge from Florida House Speaker Richard Corcoran of Land O'Lakes and possibly state Sen. Jack Latvala of Clearwater. Still, Putnam enters the race to succeed Gov. Rick Scott as the clear front-runner, having built a statewide network of donors and grass roots activists over a lifetime in politics and already sitting on more than $7 million in a political committee.On the Democratic side, former U.S. Rep. Gwen Graham, 54, has announced she will make a "major announcement" in Miami Gardens today, which is likely to be her formal entry into the race. The daughter of Bob Graham, Florida's former governor and senator, lives in Tallahassee but grew up in Miami-Dade. Tallahassee Mayor Andrew Gillum and Orlando-area businessman Chris King have already kicked off their campaigns, and Miami Beach businessman and Mayor Philip Levine is actively exploring a run.None of the Republican prospects for governor is well known. An automated poll by Gravis Marketing in late March asked Republicans about a potential governor's primary between Putnam, Latvala, former U.S. Rep. David Jolly of Pinellas and former St. Petersburg Mayor Rick Baker. Nearly two-thirds, 63 percent, said they were undecided, while 21 percent said Putnam, 5 percent Jolly, 5 percent Latvala and 2 percent Baker.A Bartow native, Putnam is a fifth-generation cattle and citrus farmer. He became a member of the Florida House at age 22, serving two terms before winning a congressional seat. He spent 10 years in Washington, becoming House Republican Conference chairman, the third-highest ranking position in the House, before winning election as Florida agriculture commissioner in 2010. That move was widely seen as positioning himself for his ultimate goal — Florida governor. He is term-limited and cannot run for re-election as agriculture commissioner.Critics and skeptics paint him as a career politician."Today Adam Putnam announced he will continue to do what he had done for the last 10 or 15 years … Run for FL Governor," state Rep. Chris Latvala, R-Clearwater, the son of Sen. Jack Latvala, tweeted after Putnam's announcement.Putnam and his wife, Melissa, have four children and live in Bartow, where he said he will hold a downtown barbecue May 10 and "share my vision for Florida's future."Contact Adam C. Smith at [email protected] Follow @AdamSmithTimes.