For the fourth time in a row Maine faces a broad scramble to succeed a two-term governor. Next year’s contest may become the most wide open since 1994.Both major party nominations could be hotly contested and a number of independent figures are under close watch as Maine’s third gubernatorial campaign under the Clean Elections system that offers a public financing option gets under way.Democrats, Republicans and Greens hold primary elections next June.Steven Rowe of Portland, a former state attorney general and House speaker, has a leg up among Democrats. Another declared Democrat is little-known state Rep. Dawn Hill of York, a lawyer and small business owner.Among Republicans, early activity was stirred by untested longshots: Matthew Jacobson, president and chief executive of Maine & Co. from Cumberland and developer Bruce Poliquin of Georgetown. Republican Les Otten of Greenwood, the former ski mogul, has formed an exploratory committee and others are waiting in the wings on both sides, so the field could grow.