Republican Pennsylvania House Speaker Mike Turzai, 58, an ally of the oil and natural gas industry, has joined a field of challengers to oust first-term Democratic Gov. Tom Wolf, who is up for re-election in 2018. Turzai, 58, a lawyer elected to the state House in 2001, became speaker two years ago and has played a major role in preventing efforts to implement and oil and gas severance tax. Wolf, who took office in 2015, has pushed hard for a severance tax. Turzai joins other GOP challengers, including State Sen. Scott Wagner, attorney Laura Ellsworth and consultant Paul Mango.