When "Supporters" (whoever they're) of Rouhani understand that neither Rouhani has any "real power" in the Islamic Republic of Iran, nor did Ahmadinejad, they will stop voting altogether there.
That’s not relevant either way, since both Rouhani and Ahmadinejad believe and espouse the same things as the Ayatollah. If they stop voting, they’ll be made to vote, just like with the last “election” in North Korea where “100 percent” of the populace “voted” for Kim Jong-un.