Marion Barry, all but inaugurated as D.C.’s next mayor, should be sweating a little after the Oct. 22 “Fight to Unite” at the Washington Convention Center that pitted former world heavyweight champion Leon Spinks against journeyman fighter John Carlo. Barry introduced Spinks to the crowd before the bout, and undoubtedly feels an affinity for the 41-year-old fighter. After all, Spinks, like Barry, rose to national prominence in 1978 by scoring a huge upset victory. (The young boxer dethroned pudgy, aging Muhammad Ali. The young politician dethroned pudgy, aging Walter Washington.) Substance-abuse problems toppled both the world champ and the Mayor-for-Life, but both surged back recently. Spinks won a few tuneup bouts and was considered a shoo-in to defeat Carlo; Barry captured the Ward 8 D.C. Council seat and the Democratic mayoral primary, and is considered a shoo-in to clobber Republican mayoral candidate Carol Schwartz in November. So Schwartz should take heart: Carlo knocked out Spinks in 69 seconds.