Washington (CNN) New York City Mayor Bill de Blasio announced Friday that he is dropping out of the 2020 presidential race, ending a campaign that failed to gain traction amid a crowded Democratic primary field.

De Blasio sought to cast himself as the most progressive candidate in the large field of Democrats vying to take on President Donald Trump, and he used his time on the national stage to attack less progressive candidates, namely former Vice President Joe Biden, for positions that he felt were out of step with the current mood of the Democratic Party.

In the end, however, de Blasio was unable to convince liberal Democrats that he was more qualified than Massachusetts Sen. Elizabeth Warren or Vermont Sen. Bernie Sanders, the two leading liberals in the 2020 race.

"I feel like I've contributed all I can to this primary election and it's clearly not my time," de Blasio said on MSNBC's "Morning Joe." "So I'm going to end my presidential campaign, continue my work as mayor of New York City, and I'm going to keep speaking up for working people and for a Democratic Party that stands for working people."

De Blasio, 58, pledged on Friday to push for progressive ideas as the Democratic primary process continues.

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