– A few days before Sunday's presidential election, several dozen Venezuelans huddled in a small church in the capital of Bogota to pray that voters "wouldn't make a mistake."

They were hoping that Ivan Duque, a 41-year-old former senator who is leading the polls, will emerge Sunday night as the winner in a country that has been one of the U.S.'s staunchest allies in the Western Hemisphere. Virtually unknown just a few years ago, Duque is presenting himself as the law-and-order, pro-business candidate who has the backing of powerful former President Alvaro Uribe.

The candidate they don't want to see win: Gustavo Petro, a 58-year-old former mayor and senator, who is campaigning from the other end of the political spectrum as a progressive reformer and anti-corruption crusader.

Petro's past as an M-19 guerrilla, and his coziness with late Venezuelan President Hugo Chavez, however, has made him toxic to the hundreds of thousands of Venezuelans who have sought refuge in Colombia as their own country has descended into economic chaos. And while Venezuelans cannot vote here, their advocacy may help push Duque over the finish line on ­Election Day.

Most polls give Duque a comfortable lead in Sunday's race. An Invamer survey released June 8, predicted he'll win 57 percent of the vote vs. Petro's 37 percent. Another poll by CELAG, however, put Petro within 6 points of Duque. Colombia's next president will have to face a series of tough issues, including implementing a fragile peace deal with the hemisphere's largest guerrilla group — the Revolutionary Armed Forces of Colombia, or FARC — containing a boom in drug crops, reducing income disparity and steadying the economy.

But along the border, the Venezuelan crisis is drowning out complex or nuanced debate, said Yolima Gomez, one of the coordinators for Petro's campaign.

"It's been very, very difficult in this area to get beyond the Venezuela issue," she said. "People here see Venezuelans sleeping on the street, or begging, and they fear that might happen here without even knowing why it's happening there."