Texas Governor Greg Abbott declined to run against Trump, as did 2016 Republican primary candidate and current senator Ted Cruz.

Elizabeth Warren, Bernie Sanders, Michael Bloomberg and Joe Biden were among the major declared candidates.

Harris County, the most populous one in Texas, spearheaded a number of innovative approaches and was the focal point of several legal challenges.

[138] Local Republican activists and officials challenged the voter-friendly measures in multiple legal actions, with mixed success.

Several lawsuits complained about early voting and about Harris County providing multiple drop-off locations for absentee ballots.

[143] On October 29 another action was filed seeking to invalidate drive-thru ballots based on the contention that this was a form of curbside voting that the Texas Election Code authorized only for voters with disabilities.

[145][146] The next day, U.S. District Judge Andrew Hanen heard an almost identical case by the same group of plaintiff, which included Republican candidates, on an emergency basis.

"[142] Hanen ruled against the plaintiffs, dismissing their action for lack of standing, with the result that drive-in voting remained in effect.

The Plaintiffs, which included Steve Toth,[147] immediately sought emergency relief in the Fifth Circuit Court of Appeals, but were unsuccessful.

Paxton then sought emergency relief from the Texas Supreme Court, which backed the Governor and lifted the temporary injunction in an October 27 decision with no dissent.

While Biden's lead in the Rio Grande Valley shrunk significantly compared to Hillary Clinton's in 2016, he overwhelmingly won the Latino vote in the state's urban areas.

[180] Biden significantly outperformed Clinton in Greater Austin, which contributed to Trump's relatively weak performance statewide.

[183] Because of Trump's substantial gains in heavily Hispanic areas, Biden's best performance in Texas came not from the southern border region, but Travis County, encompassing the college-educated, cosmopolitan, liberal bastion of Austin, home to the University of Texas at Austin, where he won the highest percentage for a Democrat since Harry S. Truman in 1948.

While not significantly outperforming Clinton in Harris and Bexar counties, he did make considerable inroads into their surrounding suburbs, thus eking out narrow wins in Greater Houston and Greater San Antonio,[184][185] the first time a Democratic presidential nominee had accomplished such a feat in the 21st century.

He also improved in diverse Alief, along Harris County's southwest border, which is heavily Hispanic, Filipino, and Vietnamese.

On the other hand, Biden continued Clinton's gains in the wealthy college-educated "Houston Arrow" suburbs in the city's west, though his improvements were significantly more minor.

Tarrant County is home to the fifth-largest city in Texas, Fort Worth, and had not been won by a Democrat since 1964, when favorite son Lyndon B. Johnson carried it.

His growth in the heavily Republican Fort Worth suburbs, which historically kept Democratic candidates from capturing Tarrant, was a critical factor in winning the county and the Metroplex as a whole.

Both of their county seats (the two suburban cities of McKinney and Denton, respectively) have trended leftward since 2016 due to the influx of younger professionals and families in the past decade, which shifted to the Democrats in this election.