Five Mainers have formally registered as candidates for governor next year, but others are leaving the door open to the idea. What is known for sure is that the incumbent, Republican Paul LePage, is in, and independent Eliot Cutler is on board to seek a rematch against LePage, whom he almost beat in 2010. The big question is whether Democratic five-term U.S. Rep. Michael Michaud will abandon his 2nd District seat and run. A familiar figure in Augusta where he served decades in the Legislature, Michaud’s entry would trigger a stampede for his congressional seat. About a dozen figures from both parties are said to be interested.