FACTBOX: Congressional scenarios in Argentine farm conflict

BUENOS AIRES (Reuters) - Argentina's Congress is expected to vote in the next few weeks on the president's contentious soy export tax hike, which has sparked a deep political crisis and three months of farmer protests.

The conflict has pushed up global soy prices, hurt Argentine bond prices, caused sporadic food and fuel shortages and damaged the popularity of President Cristina Fernandez.

Fernandez, who defends the new tax system as a way to distribute windfall profit from Argentina's top crop, tried to defuse the crisis this week by sending the tax in a bill to lawmakers.

But farmers fear lawmakers will rubber stamp the bill because the ruling party controls Congress, and they decided to continue protests, holding back grains from markets.

Here are possible scenarios in Congress.

* Fernandez's Peronist party could use its clear majority to ratify the soy levy without modifications, possibly trying to cushion the blow for rural lawmakers by passing separate laws benefiting their provinces. A ratification is the perfect excuse for farmers to extend protests, especially because many farmers demonstrating along highways are no longer listening to their leaders, who've asked them to tone down their actions. It could also spark a revival of middle-class street protests over the government's perceived inability to resolve the crisis. Although the president has asked Congress for a ratification, she could be working behind the scenes for a different outcome, so as not to provoke more protests.

* Peronist lawmakers from rural provinces could break ranks with the central government and Congress rejects the levy. This is seen as unlikely unless it is a cover for a behind-the-scenes agreement between farmers and the government. The government has been so stubborn about maintaining the tax that the president could veto this vote and send the bill back to Congress, possibly sparking further protests by farmers and the middle class.

* Lawmakers from rural areas may insist on an open debate of the bill -- modifications would then be discussed publicly and in the media -- and then it could be passed with or without changes, such as lowering the tax rate or removing the sliding-scale mechanism linked to global grains prices. Such changes could mean a victory for farmers, and protests would most likely end. But if the president vetoed changes, that could spark more protests. This outcome depends on whether momentum gathers among dissident Peronist lawmakers.

* Farmers and the government are already lobbying lawmakers, and that will continue intensely over the weekend. Farmers could move the scene of their protests from highways to outside Congress to pressure legislators.

* There could always be a surprise twist. The government has delivered several surprises during the conflict, including sending the tax scheme to Congress.

(Reporting by Fiona Ortiz; Editing by Cynthia Osterman)