Yes, you do vote again. The first vote was the primaries, where you choose the candidate to represent the party in the general election. That's one of the big changes I've made. You guys are no longer just the people, voting in the general election, you're now Senators and delegates and whatnot. You can propose big legislation and you can do what any normal Congress can do. You can run Mexico, not just watch it.
The Mexican system is almost the exact same as the American system except for some minor differences. Differences that I won't bother to get into. For all intents and purposes just assume that the Mexican political system is basically the American political system.