Colombian James Rodriguez set up the burly Brazilian who pounced on the ball down the right in the 55th minute, outpaced a defender and slotted home a diagonal shot, silencing the home fans in the 30,000 strong "Quarry" stadium.
Braga, who were just two points behind Porto going into the match, wasted several good chances with Hugo Viana and striker Lima the main culprits.
"This championship will be discussed until the end but this was an important step for us," said Porto coach Vitor Pereira.
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