The 1991 United States Senate Special election in Pennsylvania was held on November 5, 1991. Incumbent Democratic U.S. Senator Harris Wofford won the special election that was held because of the death of Republican Senator John Heinz on April 4 of that year. Wofford was appointed by Governor Bob Casey to serve as Senator until the special election which he subsequently won. Major-party candidates for this election were chosen by party committees, as the vacancy had happened too late for a primary to be held.
Wofford's win was impressive because as little as 5 months before the election, polling showed him to be trailing Thornburgh by upwards of 40 points. Both the state and national Democratic establishment was tepid toward Wofford's campaign, feeling that Governor Casey had missed a prime opportunity to select a top tier candidate and had instead created a situation where Republicans would take back the seat just months after losing it. In conjunction with his fundraising issues, Wofford also had difficulty communicating his message to the voters; because he had a bureaucratic as opposed to a political background, he spoke in a somewhat long-winded manner that received criticism in the media. With his large lead in the polls, Thornburgh laid back to avoid mistakes, which allowed Wofford to gain traction. Despite his elite upbringing, Wofford connected well with working class voters as he made access to healthcare a huge plank of his campaign. He also successfully derided Thornburgh for his connections to the president, as Bush's popularity was steeply declining due to a recession.
Thornburgh was unable to mount credible attacks against Wofford until after the Democrat had already established himself. As a result, Wofford was not only victorious in traditionally Democratic areas, such as Philadelphia city, Scranton, and metro Pittsburgh, but he also ran well in GOP strongholds. Wofford won three of the four suburban Philadelphia counties, which, although socially liberal, were strongly aligned with Republicans; the "roll-up-your-sleves" style campaign ran by Wofford also allowed him to perform stronger than most Democrats in rural regions and to even win several usually Republican counties with a strong labor base.