God did not harden His heart at the begging,, God knew however that Pharoah would harden his own heart and therefore told Moses that God would Keep Pharaohs heart hardened to a deluded extent.. Any sane ruler would have known they where dealing with a God they had no hope of opposing by the time the third and latter plagues happened but God sent pharoah strong delusions..
God will do this in the future and for the same reason .. People hardening their hearts against the gospel message we read in the NT that in the end times::
2 Thessalonians 2: KJV
1 "Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him, {2} That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand. {3} Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition; {4} Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God. {5} Remember ye not, that, when I was yet with you, I told you these things? {6} And now ye know what withholdeth that he might be revealed in his time. {7} For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way. {8} And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming: {9} Even him, whose coming is after the working of Satan with all power and signs and lying wonders, {10} And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved. {11} And for this cause God shall send them strong delusion, that they should believe a lie: {12} That they all might be damned who believed not the truth, but had pleasure in unrighteousness."
So again we shall see God causing those who reject his will to be deluded and fall victims to end times satanic deception.. Because they rejected the Love of the truth ( Gospel ) that would have saved them..