HARRISBURG, Pa. (AP) - Gov. Tom Wolf's administration and its allies are working to sway enough rank-and-file House Republicans behind a $1 billion-plus tax increase to override opposition from House GOP leaders and end the five-and-a-half month budget stalemate.

House Speaker Mike Turzai set a 12:30 p.m. Thursday deadline for the Democratic governor to show he could assemble enough votes to move the tax package through the chamber.

Wolf and House Democratic leader Frank Dermody are downplaying Turzai's 24-hour ultimatum, but rank-and-file House Republicans say it'll be a challenge to persuade 20 or 30 of them to support the tax increase.

The tax plan continued to evolve Wednesday night.

Wolf wants the tax increase to undo his predecessor's funding cuts to education and human services and to narrow a long-term budget deficit.