Conservative opposition candidate Luis Lacalle Pou is leading in the polls against ruling party candidate Daniel Martinez after striking key coalition deals following a first-round vote in October.
The likely political shift in the country of 3.5 million people comes amid a series of shocks in the region, with neighboring Argentina pivoting back to the left, Bolivia convulsed by political crisis and Chile's right-wing government being hammered by protests.
In Uruguay the rise of the opposition National Party to the long-standing ruling coalition follows a slowing economy and rising fears about crime. The party leads a coalition of five mostly conservative parties.
Those alliances are proving key. Lacalle Pou came second in the Oct. 27 vote with around 29% of the vote, behind Martinez's Broad Front with 39%. Pollsters see him winning Sunday's head-to-head with the votes from his new allies.
Security and growth are central for his support base. While still growing, Uruguay's farm-driven economy has slowed markedly and was up 0.1% in the second quarter.
"Lacalle is the president who can improve the country, change what Broad Front did wrong economically and especially security," said Mariela Barcia, a 51-year-old teacher who voted for Lacalle Pou in October.
Daniel Nunez, a 27-year-old student, voted in October for the Colorado Party, now allied with Lacalle Pou, and said he would back the opposition leader.
"I think it is good for democracy that there is a change of government. There are many things that Broad Front has done well and others very badly, so I hope we change to improve what is wrong," said Nunez.
Pre-election forecasts vary, but all major opinion polls show Broad Front falling behind.
Pollster Cifra, in its most recent survey, handed Lacalle Pou 47% of the vote and Martinez 42%. Consultancy Factum had a wider split of 51% against 43%.
Supporters of the socialist-leaning current administration are concerned that state support could be pulled back under a conservative leader."I don't forget what this government did for the retirees, for the young people. I don't know if all that is going to be maintained with Lacalle," said Marisa Perdomo, a 63-year-old retiree, who will vote for Martinez.