What Party would Robert Casey Sr. be part of today?

[The Govanah Jake]

Probably Democrat. He may of been a conservative on Abortion and other civil issues however that would not necessary make him a Republican. From what i can find i think he could just quite as well be a Social Moderate-Conservative and Fiscal Liberal-Moderate Democrat and could find a home with similar democrats like the Blue Dogs.
Here is from Wikipedia below on his Fiscal Policy in Pennsylvania. Dont think it is quite what a republican would do:

"Casey brought what he called an "activist government" to Pennsylvania, expanding health care services for women, introducing reforms to the state's welfare system, and introducing an insurance program for uninsured children (which became a model for the successful SCHIP program later adopted nationwide). House Bill 20, entitled the Children's Health Insurance Act, created the Children's Health Insurance Program (CHIP) in Pennsylvania. According to PA's CHIP website, "Pennsylvania's CHIP program would later be used as the model for the federal government's SCHIP program. Legislation for the federal CHIP program was signed into law August 5, 1997 by former President Bill Clinton." ".