Extremely DUMB move to resign if you didn’t do anything wrong, though expected considering how weak and no-pulse European left tends to be. I get doing it if you know you’re guilty and is a matter of time to be caught, so you want to take your body out of the center of attentions. So when Costa resigned, I thought he might be guilty but still had the possibility of European Left being European Left again in the back of my mind.
Given President Marcelo has the unilateral authority to call a snap election, and I suspect he’d have triggered it if Costa failed to resign, I don’t think it really matters.
The real question for PS is whether Costa would perform better than a new leader in snap elections, and given the state of his cabinet that doesn’t seem likely, so he probably needed to be disposed of.
And the tens of thousands of cash seized from his chief of staff’s office indicate even if this was a mistake he’s got something murky going on.