I am rather too preoccupied with the smoke and ash around the finca to have much to say here, but…
Elections for president and congress in Argentina are today.
The president is elected by qualified plurality: 45% suffices for a first-round victory, as does a plurality of between 40% and 45%, as long as the runner-up trails by at least 10 percentage points. There is probably no doubt that the next president will be the wife of the current Peronist one (Kirchner). Is there any chance of a runoff? Doubtful, I think. (There has not been a runoff since the current rules replaced an electoral college in 1995, though there should have been once: In 2003, the Peronists split and presented several candidates, but the number two candidate, former president Carlos Menem withdrew, and the runoff was never held. Nestor Kirchner became president on around a quarter of the votes.)
Argentina is the only country in the world to have staggered terms for its lower house (as far as I am aware). In each province, half the deputies will be elected today (plus or minus one in the case of odd numbers). Closed-list PR.
There are also elections for federal senators in some (half?) of the provinces. Closed-list plurality with limited nominations (i.e. two candidates nominated per party, with the plurality electing both and the second party electing its first-ranked candidate).
I hope some readers can fill in details or offer corrections in the comments. This is all off the top of my rather hazy head.