Impeachment Talk in Brazil

Boz writes about impeachment talk in Brazil. Gossip is gearing up bigtime: Dilma wanted to commit suicide! She won't last! Don't invest! Brazil should adopt a parliamentary system (though remember it already voted against it before)!

There are countless articles mentioning impeachment, but they don't actually ask why it would be possible. That's not even clear for Brazilian analysts.

If you're curious, here is the relevant portion of the Brazilian constitution (their English translation).

SECTION III
Liability of the President of the Republic
Article 85. 
Those acts of the President of the Republic which attempt on the Federal Constitution and especially on the following, are crimes of malversation: I – the existence of the Union; II – the free exercise of the Legislative Power, the Judicial Power, the Public Prosecution and the constitutional Powers of the units of the Federation; III – the exercise of political, individual and social rights; IV – the internal security of the country; V – probity in the administration; VI – the budgetary law; VII – compliance with the laws and with court decisions. These crimes shall be defined in a special law, which shall establish the rules of procedure and trial. 

Article 86. If charges against the President of the Republic are accepted by two thirds of the Chamber of Deputies, he [sic!] shall be submitted to trial before the Supreme Federal Court for common criminal offenses or before the Federal Senate for crimes of malversation. The President shall be suspended from his functions: I – in common criminal offenses, if the accusation or the complaint is received by the Federal Supreme Court; II – in the event of crimes of malversation, after the proceeding is instituted by the Federal Senate

The question I have is whether the major Petrobras scandal is impeachable at all because Rousseff was not president at the time. I would think her removal would only be possible if the corruption was linked to her presidency (say, her re-election effort) but that'll be up for debate.

What the opposition may well do is push the idea of impeachment as far as possible, such as publicly trying to gather the necessary 2/3 votes in the lower house, which if my math is correct would be 344 votes. In the Chamber of Deputies there are 29 parties in 16 blocs. There is lots of talk but actually getting those votes is a different story. Nonetheless, it creates public pressure, which might be augmented with protests. Will a combination of scandal, protests, impeachment talk, abysmal approval ratings, and a weak economy be enough to force resignation?