She was the presidential candidate for Social Democratic Party (Mexico) during the 2006 elections, obtaining 2.7% of the popular vote, which was enough to secure the party's national registration.[4] Her campaign was considered particularly successful, considering she ran without any private or public funding. The first presidential debate during the campaign is considered her best performance.
On 2014, she was appointed Secretary of Labor of Mexico City, and in 2015, as Secretary of Government in Miguel Ángel Mancera's administration. Between 2018 and 2024, Mercado was senator by National List. Since 2024, she is federal representative by proportional representation.