MONTEVIDEO, Uruguay (AP) — The center-left coalition that has governed Uruguay for 15 years is going into Sunday's presidential election as the front-runner, but spreading unease among voters is feeding a strong challenge from a bloc of opposition parties that is expected to force a second round.

The governing Broad Front has campaigned on its social agenda of improving life for the poor, allowing gay marriage and creating the world's first national marketplace for legal marijuana.

The opposition coalition has capitalized on growing disenchantment over slower growth and rising insecurity in the South American nation of 3.4 million people.

Analysts say neither of the top two contenders among 11 candidates has enough support to secure a victory in the first round, setting the stage for an eventual runoff in November.