According to Ecuador's National Electoral Council, with 7.4 percent of the votes counted, Arauz is ahead of the other candidates with 33.02 percent support. Meanwhile, conservative candidate Guillermo Lasso, who is expected to face Arauz in the runoff, has 19.22 percent.
The runoff is set for April 11. To win in the first round, a candidate would need to get 50 percent plus one vote, or 40 percent with at least a 10-point lead over the nearest contender, which appears unlikely.
Ecuador held a general election on Sunday, choosing a successor to socialist President Lenin Moreno and electing lawmakers to the National Assembly.
Exit poll data showed that Andres Arauz, a candidate from the Union of Hope (UNES) coalition of left-wing parties, had more than 30 percent of the votes, while Guillermo Lasso, from the CREO right-wing movement, had around 21 percent.
The Union of Hope has already declared victory without waiting for the official results.