According to the dramatic reenactment, why did Harry Burn change his vote?

He changed his vote because of a letter from his mother asking him to "be a good boy" and vote for the amendment.

Explanation:

Harry Thomas Burn was the youngest member of the state legislature (Tennessee General Assembly) He is remembered for the step taken to ratify the Nineteenth Amendment during his very first legislature. Even though he really intended to vote for the amendment, he was pressurized by party leaders and other misleading telegrams. He began to side with the Anti-suffragists. He received a letter from his mother which made him to change his mind and vote for the amendment. The result of the vote was a tie of 48-48, when the house speaker called for a vote on the "merits", but his vote broke the tie in favor of ratifying the amendment.