A conservative think tank introduced a proposal to phase out Maine’s income tax, one of the top priorities of Governor Paul LePage, a Republican. The Maine Heritage Policy Center is promoting the plan as a bipartisan idea that will spur growth in economically hard-hit areas. The center will lobby lawmakers to take action next year. Scott Moody, chief executive of the think tank, said the plan embraces a philosophy developed under Governor John Baldacci, a Democrat, that offers tax cuts for companies in certain sectors, such as biotechnology, with the aim of helping those businesses grow. The new plan would apply that to individuals and eliminate the income and sales taxes first in Maine’s most impoverished county, Washington, and gradually statewide.