Valencia has made the largest gain since February but still trails Cepeda significantly, while other candidates remain below 4% in first-round projections.
Cepeda, an ally of President Gustavo Petro, strengthens his position five weeks before the election, suggesting a likely victory over conservative rivals in a potential runoff.
Will the anti-Petro vote unite to block a second leftist term?
Polls favor Cepeda, but markets bet on Valencia. Who will really win Colombia's presidency?
How will Colombia's next president navigate a relationship with Donald Trump?
Will Colombia's election trigger a market boom or a financial crisis?
Can a Bukele-style 'iron fist' populist reshape Colombian politics?
Is Colombia's fragile 2016 peace accord on the brink of collapse?