Catherine Baker Knoll won a narrow and surprising victory to become Rendell's running mate.
However, Allen Kukovich, a fellow senator from a Pittsburgh exurb, launched a vocal challenge to Wagner, that opened an ideological split within the party.
Wagner ran as a traditional moderate with strong union ties, while Kukovich portrayed himself as a liberal.
Knoll, a long time fixture in state politics, took advantage of the split and, using her strong support among women and senior citizens, scored an upset win.
Jane Earll, a State Senator from Erie was unopposed for the Republican nomination and thus became Fisher's running mate.