Petrobras (PBR) shares were in a steady uptrend this year that looks like a swing traders dream with waves of higher highs and higher lows after the giant integrated Brazilian energy company finally bottomed at a multi-year low of $10.

But early September's peak just below $21 was met with some fast and furious liquidation bringing shares back nearly 25% in a couple of weeks.

The cause? More earnings estimate revisions (EER) of the downward variety. And this is not a new story for PBR since the shares traded back above $50 in late 2009.

Here is the Zacks proprietary Price & Consensus chart that shows how well stock prices following the direction of EER...

The Brazil Economy and Politics

Some energy analysts probably also cite larger macro forces at work in shares of PBR too. Brazilian stocks had a remarkable bull run this year that PBR was part of.

But more recently, Brazil's equity market has been riding the election waves. When the polls show voter support for incumbent Dilma Rousseff, markets sell off, while improving prospects for opposition candidate Marina Silva sends the iBovespa index higher.

In this Latin American nation, leftist President Dilma Rousseff has come under heavy criticism for Brazil’s dismal economic performance under her leadership, highlighted by recession and increasing inflation. Therefore, her re-election is perceived as the extension of this ‘stagflation’-like situation.

On the other hand, Brazilian Socialist Party presidential candidate Marina Silva is seen as increasingly pro-industry, thereby preferred by investors. The business community is hopeful that her win would not only attract more capital to the country but more importantly, reduce the state intervention in company affairs.

Watching the coming October 5 election results will be important for PBR investors. But equally vital will be monitoring the Zacks Rank to tell you when the analysts have turned around their view of the company's earnings outlook.