Concerning the carrying of a handgun, either openly or concealed, at a polling place, the law is silent on such. Ergo, ipso facto, etc., if it's not illegal then, by default, it's legal.
Now, if the polling place is in a K-12 school facility, 18 Pa. C.S. 912(b) comes into play with illegalizes the carrying of firearms on school property. 18 Pa. C.S. 912(c) makes an exception for other lawful purposes. Since either open or concealed carry (with an LTCF) may well be argued to be for a lawful purpose, i.e., self-defense, this appears to be an exception. Supporting concealed carry is the License to Carry Firearms in which self-defense is specifically listed as a reason for issuance, hence a lawful purpose.
I suppose there have been numerous cases of people getting cited for 18 Pa. C.S. 912(b) violations when they were openly carrying, but, according to my state representative (Sam Smith - Punxsutawney),there have been only two such cases where LTCFs were involved - Bolden v. Chartiers and Commonwealth v. Heidler, neither of which directly addressed the issue.
I'm not an attorney, nor do I want to be one, but I do believe no district attorney wants to touch a 912(b) case if the bearer possesses an LTCF - too much of a chance of getting bitten hard by that pesky "other lawful purposes" clause.
Bottom line (my opnion) - concealed means concealed, and open carry at a polling place held in a K-12 school is asking for trouble.
No penalty flags on this one - applicable state law and court cases were listed.