As Texas voters head to the polls in the Democratic primary on Tuesday , the second-largest stash of national convention delegates hangs in the balance.

But beyond the top of the ticket, where Sen. Bernie Sanders (I-Vt.) is battling a resurgent former Vice President Joe Biden for dominance, the state is also due to host the most closely watched Democratic House primary of the 2020 election cycle.

In South Texass vast 28th Congressional District, progressive immigration attorney Jessica Cisneros , 26, is hoping to unseat conservative Democratic Rep. Henry Cuellar , who is 64. Cuellars history of opposition to abortion rights, gun regulation and tougher union protections, as well as his support for the fossil fuel industry and some of President Donald Trump s immigration policies, have earned him the enmity of an array of labor unions, reproductive rights and progressive groups.

Although Cisneros has raised more than any of Cuellars challengers in recent memory and she enjoys the support of some of the countrys leading progressives including Rep. Alexandria Ocasio-Cortez (D-N.Y.) and Sens. Sanders and Elizabeth Warren (D-Mass.) most observers maintain that she is in a tough fight.

Thats because Cuellar, an eight-term incumbent, leads a family that dominates politics in the border city of Laredo and benefits from the largesse of the national Democratic establishment as well as deep-pocketed corporate interests and ideologically conservative groups. He also holds power in a heavily Roman Catholic, Latino region where the typical voting population has more socially conservative leanings; the growing contingent of young Latinos with more liberal views, as well as more impoverished residents, are more likely to sit out elections.

Since Cisneros has generated more attention and resources than any of the lefts congressional primary challengers this cycle, a loss would be disappointing. The regions conservative bent would make her win that much more transformational, however and inspire fear in incumbent Democrats across the country.

A win for Cisneros would show that progressivism, as exhibited by Ocasio-Cortez, can even reach into the recesses of South Texas, said Texas politics expert Terence Garrett, who chairs the public affairs department at the University of Texas Rio Grande Valley. It would be a dramatic shift.

The race is also a bellwether for Democrats hoping to turn Texas blue, according to Garrett. Higher-than-normal participation from young people and other infrequent voters in the low-turnout region would benefit Cisneros and Sanders but also portend well for Democrats chances of bringing the state into the partys column in November, he predicted.

Young Latino turnout is key, he said.