During her first term, Brazilian president Dilma Rousseff had a discreet number two in Michel Temer.

Behind closed doors her 75-year old vice-president is a skilful negotiator in the country’s raucous political marketplace. But in public he never seeks the limelight.

His image is that of a stiff constitutional lawyer who, like many elderly members of Brazil’s elite, dabbles in poetry, though on state occasions the gravitas he clearly seeks to project is undone somewhat by the presence of his trophy second wife, 43 years his junior and with his name tattooed on to the back of her neck.

But now that Rousseff's popularity has imploded since her re-election to a second term Temer has turned on her. Rumour had it he was plotting in the shadows for months, though rarely speaking out publicly so that when he did so, as in August when he said Brazil needed someone to "reunify" the country, his few cryptic words caused a political storm.

With the head of the lower house of congress Eduardo Cunha having initiated impeachment proceedings against Rousseff, Temer has formally broken cover. In an explosive personal letter to the president, strategically leaked to the media as she read it, Temer accused her of treating him as a "decorative vice" who she felt free to ignore even though he was head of the Brazilian Democratic Movement party (PMDB), the country's biggest party and main pillar of her governing coalition.

Act of revenge

Though Cunha, also of the

PMDB

, had his own reasons for launching the impeachment process – it was a naked act of revenge after the president’s Workers Party said it would support efforts to oust him over his involvement in the

Petrobras

mega-scandal – her supporters wonder about his long-standing relationship with Temer and what encouragement the latter provided for his move against the executive.

Last week Cunha's bid to shape the impeachment process so as to cause maximum political damage to the president was derailed by the supreme court and he will likely be expelled from congress over revelations he keeps millions stolen from Petrobras hidden in bank accounts in Switzerland before it even begins to debate Rousseff's mandate.

That still leaves the vice-president and his ambitions to ascend to the top job in play. The basis of his bid is Rousseff’s massive rejection rating. Having lied about the parlous state of the economy to secure re-election she has seen voters turn on her. Two-thirds of Brazilians consider her administration “bad” or “very bad”.

Unfortunately for Temer the same polling company shows 58 per cent believe he would be “as bad or worse” should he replace her.

But last week’s supreme court rulings that were so damaging to Cunha also knocked Temer’s hopes as it switched the focus of the impeachment battle from the lower house to the senate. The chamber of deputies is consumed by a civil war between Dilmistas and Temeristas.

Decide her fate

But her position remains relatively secure in the senate, the less-than-august body whose 81 members – at least 30 of whom are being investigated or have been charged with corruption, 14 in the Petrobras case alone – will now decide her fate.

Here Rousseff has a powerful ally in senate president Renan Calheiros who is now leading the battle within the PMDB against impeachment and Temer.

Himself facing multiple accusations before the supreme court – which in an apparent show of cowardice has sat on some of the charges for nearly a decade – Calheiros is one of Brazil’s most corrupt, and hence loathed, politicians. That he is riding to the rescue of the left shows how far off course the Workers Party’s political project has blown.

All Brasília knows Calheiros's price for his services: more power and position for his clique, for years at or near the centre of many of the country's endemic corruption scandals. And it comes with a buyer-beware clause. If he senses even his help cannot save the president he will abandon her. He is little more than a cut-throat trader in Brazil's volatile political market.

That should stand as a warning to Rousseff who all year demonstrated a remarkable habit of winning the defeat. There have been plenty of tactical victories marking her administration’s long march towards economic, judicial and institutional chaos. Maybe now that the stakes have grown so large she will finally start displaying some political nous. But few would wager much on it.

Temer might be on the back foot for now but his moment could yet come.