Did God make Pharaoh harden his heart?
No, God did not make Pharaoh harden his heart. Although Scripture says God hardened Pharaoh, the word usually means heavy: the more Pharaoh opposed God, the more God's wrath weighed on him. God placed Pharaoh where he could accept or reject, and by rejecting, Pharaoh hardened his own heart.
Les explains that hardeneth in Scripture is usually translated heavy, as when Isaiah spoke of a burden that was heavy. The more Pharaoh tried to oppose God, the more the weight of God's wrath weighed down on him. Pharaoh, like anyone today, came to that place of hardening his own heart, not because God made him do it, but because God put him in a place of either accepting or rejecting, and by rejecting he hardened his own heart. Even though Scripture says God hardened, men are not lost because they are hardened; they are hardened because they are lost.
Therefore hath he mercy on whom he will have mercy, and whom he will he hardeneth.