Mexican independent candidate and former first lady Margarita Zavala says she is dropping out of the country's July 1 presidential race.

Zavala had broken her longtime affiliation with the National Action Party and qualified for the ballot as an independent. But she has been polling in the single digits, far behind the leading candidates.

Zavala made the announcement Wednesday. She said she was withdrawing "on the principle of political honesty and a sense of congruency," and to free her supporters to "make the decision they need to make in this difficult race."

Zavala's husband, Felipe Calderon, was president from 2006 to 2012.

Four other candidates remain on the ballot.