Presidential candidate Bernie Sanders is wading into one of Texas’ most closely watched primary challenges, endorsing progressive candidate Jessica Cisneros who has mounted a bid to unseat U.S. Rep. Henry Cuellar, D-Laredo, one of the most conservative Democrats in Congress.

“This is the most important election in our lifetime and I’m proud there are so many candidates running for Congress who understand that real change comes from the bottom on up, not the top on down,” Sanders said in a statement.

Cisneros was one of nine candidates Sanders endorsed early Wednesday, in addition to incumbent Democratic Reps. Ilhan Omar of Minnesota and Peter Welch of Vermont.

Some progressives had weighed in wondering why Sanders had not endorsed Cisneros earlier while she collected a number of high-profile endorsements, including from fellow presidential candidate Elizabeth Warren and U.S. Reps. Ayanna Pressley, D-Massachusetts, and Alexandria Ocasio-Cortez, D-New York.

Justice Democrats, the progressive group famous for helping elect Ocasio-Cortez, also endorsed Cisernos last year.

Cuellar campaign spokesman Colin Strother brushed off the Sanders endorsement as out-of-state meddling by Democrats unfamiliar with the South Texas district.

“While our opponent focuses on out-of-district and celebrity endorsements, we are focused on endorsements from people who actually live and work in the district,” Strother told The Texas Tribune. “That’s why we have over 225 local elected officials endorsing Henry Cuellar for reelection.”

The endorsement comes as Sanders ramps up his campaign in Texas ahead of Super Tuesday on March 3. On Tuesday, his campaign unveiled plans for a $2.5 million TV ad buy across Texas and California — another delegate-rich Super Tuesday state — and told The Texas Tribune that it has staffed up in the Lonestar State with five regional field directors. The campaign is also dispatching a top surrogate — national co-chair Nina Turner — to Houston this week.

“I’m so grateful to receive the endorsement of Senator Bernie Sanders who is running a grassroots campaign to fight for working people, not big corporate donors,” Cisneros said in a statement. “We’re proud that presidential candidates are taking a close look at South Texas as we fight to turn Texas blue in November — and that they know we’re the only candidate in this race who will champion Democratic values in Washington.”