[EDITOR’S NOTE: This story has been corrected to fix the political affiliation of U.S. Sen. Bernie Sanders.]

MISSION, Texas (Border Report) — U.S. Rep. Henry Cuellar, a nine-term incumbent, is trying to hold on to his party’s nomination following an FBI raid at his home and offices in January.

He has not been charged with a crime, but his Democratic challenger in Texas’ 28th Congressional District primary election, Jessica Cisneros, has highlighted the raid in TV campaign commercials.

Cisneros, 28, is an immigration lawyer who interned for Cuellar years ago. She says Cuellar has been in Washington, D.C., “too long” and has become part of the establishment. Her campaign stresses “Medicare for all” and she is trending among younger voters, political watchers say.

Cisneros ran against Cuellar in 2020 and is backed by the powerful Justice Democrats pact, which has made this seat a priority to take away from Cuellar.

She is endorsed by progressives U.S. Sens. Bernie Sanders, an Independent from Vermont; Elizabeth Warren, D-Massachusetts, and U.S. Rep. Alexandria Ocasio-Cortez, D-New York. Ocasio-Cortez campaigned for Cisneros earlier this month in San Antonio, which is part of the contested congressional district.

Prior to her Feb. 12 visit, Ocasio-Cortez tweeted, “This one’s going to be special.”

Cuellar has said he was “fully cooperating with law enforcement” regarding the investigation. However, no details have been released.

Cuellar is one of the most degreed members of Congress, having earned a master’s degree, doctorate and a law degree. And he is vice chairman of the powerful House Appropriations Homeland Security Committee.

But he also is one of the most conservative Democrats, openly opposing abortion and frequently siding with Republicans.

Cisneros came within four percentage points of unseating Cuellar during the last primary election.

“She came pretty close in 2020 to winning the primary against him,” Natasha Altema McNeely, associate professor in the political science department at the University of Texas Rio Grande Valley told Border Report on Monday.

“It’s rare (to unseat an incumbent) but the organizations that have been backing Cisneros were backing AOC,” McNeely said.

Cuellar has over the years built a heavy war chest, which Danny Diaz of LUPE Votes, a political arm of La Union del Pueblo Entero, says now Cuellar is being forced to spend in order to save his seat.

“The FBI investigation weakened Henry Cuellar in terms of money,” Diaz told Border Report on Monday. “He started having to spend money from his own war chest which is great for Jessica.”

LUPE Votes has endorsed Cisneros, whom Diaz says most is in line with the Chicano organization’s “We The Pueblo” campaign.

The campaign is “to find a community leader ready to fight for working class South Texans,” according to the organization’s website. Issues that the organization says Cisneros aligns with them include her support of Medicare for all; reducing climate change; increasing wages in South Texas; free public college education’ and a pathway to citizenship for migrants.

In a Feb. 8 tweet, LUPE Votes said Cisneros, as well as Democratic Texas Congressional District 15 nominee Michelle Vallejo, “are changing the way we do politics in South Texas. Let’s make sure we send them to congress, and finally have real representation!”

Cuellar’s campaign says he has received the endorsement of nearly 200 elected officials in South Texas, including 43 in Starr County and 78 in Webb County, where his hometown of Laredo is located. His campaign says that over the years he has helped to procure “hundreds of millions of dollars” for District 28 and this month was named a “Top 25 Policy Influencer” by Opportunity Zone magazine.

The district currently includes a portion of western Hidalgo County, including the town of Mission, however, the Texas Legislature redrew the boundaries during the third and last special session, which was called by Gov. Greg Abbott, and the district no longer includes this area.

Cisneros has raised over $700,000 in 2022 and in a statement, earlier this month said, “our movement is ready to finish what we started two years ago and I am so proud of the momentum we’re building here in South Texas.”

Cuellar tweeted Feb. 14 “the stakes are high in this election … together we will win.”

Both sides declined interview requests with Border Report.