ALTOONA, Pa., April 11 — In what was already proving a surprisingly tight contest, the race for governor of Pennsylvania has grown more complicated with the entry of an independent candidate who helped spearhead a grass-roots insurgency last year against the state legislature. The development is the latest twist in a campaign where the Democratic incumbent, Edward G. Rendell, once considered a shoo-in for re-election, has been polling neck and neck with his Republican challenger, the former football star Lynn Swann, a political newcomer. The latest arrival in the race is Russ Diamond, a businessman who last July founded PACleanSweep,...