The SEIU's endorsement, due to be formalized at a Nov. 6 meeting of its 63-person executive board, would shift the labor winds decisively to Dean. He could get an even bigger boost if the 1.3-million member American Federation of State, County & Municipal Employees swings behind him. AFSCME President Gerald W. McEntee considered backing Senator John F. Kerry (D-Mass.), then flirted with retired General Wesley Clark. But insiders say Clark's early missteps soured McEntee, who was the first major union leader to back Bill Clinton in 1992 and who wants to play kingmaker again. McEntee was miffed when Clark decided not to campaign actively in Iowa, where AFSCME's 28,000 members spread across all 99 counties could make a crucial difference in the Jan. 19 caucuses.