President Dilma Rousseff is scrambling to hold together her crumbling ruling coalition. Aides say she is negotiating key government posts with remaining allies, as key partners discuss abandoning her amid impeachment proceedings. The Progressive Party, a coalition ally, has planned for a meeting to decide whether to leave. 

The game is not over - but it's looking increasingly more difficult for president Dilma Rousseff to avoid impeachment after Brazil's largest party and key coalition member - the PMDB - decided Tuesday to pull out of her ruling coalition.

The deepening crisis prompted President Rousseff to cancel her trip to Washington for the Nuclear Security Summit. The sense here is that she wanted to take no chances - with vice-president and PMDB leader Michel Temer filling in on presidential matters  - even for just a couple of days.

Now Rousseff and her allies need to secure at least one third of the 513 votes in parliament in order to block the impeachment process.

And analysts say that leaves her little time or energy to deal with the country's growing problems - which in turn fuels increasing unpopularity.

The government is expected to try to trade ministries and top government positions left open by the PMDB for support from smaller parties in parliament. But a growing anti-Rousseff movement and the worsening economic situation are making it very risky to be on the government's side right now.

Speaking on CCTV's program, The Heat, Brazilian experts said an impeachment could set a troubling precedent for vice-president Michel Temer - should he assume the presidency - or for any future Brazilian leader.

A vote on the impeachment of Dilma Rousseff could happen as soon as mid-April if the opposition has its way. Or the process could drag on for months if the government manages to stall it. The only thing certain right now is that nothing is certain in Brazilian politics.