Former Vice President Joe Biden visited Dallas on Monday to collect a few major campaign endorsements from some of his former Democratic primary competitors.

Former South Bend Mayor Pete Buttigieg, Minnesota Sen. Amy Klobuchar, and former Texas congressman Beto O’Rourke all suggested Biden would propel down-ballot Democrats to victory in politically moderate regions of the country. O’Rourke specifically said Biden would help Texas Democrats win the nine seats they need to reclaim the state legislature for the first time in decades.

“You, Mr. President, as the top of the ticket, can help us do that,” he said.

Because growing Black and Latino communities in Texas mark a demographic shift in the state, many pollsters believe Texas is a toss-up to swing either Republican or Democrat in the 2020 elections and for years to come. For the former candidates, a Biden endorsement is key for a new blue wave.

But recently compiled data and analysis show Texas Democrats face structural obstacles to victory that Biden alone cannot fix, including the closures of hundreds of polling places in counties with large or growing Black and Latino populations.

Erich Schlegel via Getty Images A sign shows the way to the polling station at Austin Community College on Nov. 4, 2014 in Austin, Texas. Voters headed to the polls today to decide a number of tight races.

A 2019 report from The Leadership Conference Education Fund (LCEF), a civil rights organization, reveals Texas officials began rapidly decreasing the number of polling places in these counties with significant communities of color around the time the Supreme Court overturned a key provision of the Voting Rights Act in 2013. The provision, Section 4 of the Voting Rights Act, required certain states with histories of racist voting practices to get clearance from the federal government before closing polling places or changing their voting laws.

Furthermore, analysis reported by The Guardian found that the 50 Texas counties that gained the most Black and Latino residents between 2012 and 2018 closed 542 polling sites over that span, while the 50 counties that gained the fewest Black and Latino residents during that time only closed 34 sites.

“This is despite the fact that the population in the former group of counties has risen by 2.5 million people,” The Guardian reports, “whereas in the latter category the total population has fallen by over 13,000.”

Two Texas counties ― Somervell County and Jackson County ― rank in the top 10 in the nation in percentage of polling places closed since the Supreme Court’s Voting Rights Act ruling. And when looking at the total number of polling places closed nationwide, six of the 10 counties with the most closures are in Texas, according to the LCEF report. The organization found Texas closed 750 polling places statewide following the Supreme Court decision.

Texas is one of several states that allows the use of “vote centers” in place of regular polling sites. One major difference between a vote center and typical polling places is any voter can cast votes at a vote center, regardless where they live, whereas voters are assigned polling places by the county. For that reason, vote centers are sometimes seen as a convenient alternative to typical polling places. But in Texas, counties can close several polling places and erect only few vote centers in their place.

“While generally intended to enhance access to voting locations, this model often leads to massive reductions in polling places,” the report says, adding that contrary to the period when the Voting Rights Act was in full effect, Texas officials are now not required to determine whether the changes impose disparate impacts on Black and brown voters.

A spokesperson for the Texas Democratic Party said the raft of polling place closures in diverse communities are attempts by conservative election officials to shrink and restrict the electorate.

“People have died to fight for the sanctity of the vote,” the spokesperson, Abhi Rahman, told HuffPost.

“Republicans’ only way to retain power is to basically curb the vote, and we’re fighting back against all of those attempts,” he added.

Rahman said the Texas Democratic Party is conducting the “most expansive voter protection program in Texas Democratic Party history” in partnership with the organization Fair Fight, a voting rights group founded by former Georgia gubernatorial candidate Stacy Abrams.

“We have an around-the-clock voter protection team working to fight back and make sure voting is more convenient than it ever has been in the past,” Rahman said.

CORRECTION: A previous version of this article said that three Texas counties were among the top 10 in percentage of polling places closed. The study apparently labeled a county as being in Texas that was in fact in Georgia.