HARRISBURG, Pa. (AP) -- Two state senators, one a Republican and the other a Democrat, are planning to introduce a bill to legalize marijuana for medicinal use in Pennsylvania. Sens. Daylin Leach and Mike Folmer were preparing to give details of the upcoming bill Monday. The National Conference on State Legislatures says 20 states have some sort of public medical marijuana program, including two, Colorado and Washington, that allow it for personal consumption. New Jersey and Delaware have medical marijuana laws, while Maryland allows academic medical research centers to dispense marijuana to sick patients. Gov. Tom Corbett's office has said he'd veto any marijuana legalization bill, even if it were limited to medical uses, because he believes marijuana is a "gateway drug" whose use leads to more dangerous drugs.