New York Democratic Rep. Alexandria Ocasio-Cortez gave her coveted endorsement Thursday to Abdul El-Sayed, a progressive Senate candidate in Michigan who party leaders have worried might be too left-leaning to win in the swing state.

Alexandria Ocasio-Cortez backed Abdul el Sayed in Michigan, in a blow to Democratic Party leaders who have picked more centrist candidates.

The congresswoman’s endorsement marks the first time she is taking a side in a contested Senate primary.