Sen. Kamala Harris is increasingly positioning herself for a what is expected to be a crowded Democratic primary for the White House in 2020.

The former California attorney general, who is just at the beginning of her second year in the Senate, is taking positions that could endear herself with the Democratic base while allowing her to stand out from a group of Democrats who might seek the progressive mantle.

Harris voted against a Senate immigration bill backed by centrists from both parties earlier this month, waiting until the last minute to break with other liberals including Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.), who both backed the measure.

She argued that while the bill would provide a pathway to citizenship for young immigrants who entered the country illegally, it was a step too far because of the inclusion of money for President Trump’s wall on the Mexican border, and that she could not support it in good conscience.