FORT WORTH, Texas (AP) — Republican Sen. Ted Cruz, of Texas, sought to fend off an underdog challenge Tuesday from Democratic Rep. Colin Allred in one of the year's most expensive races, which is testing shifts in America's biggest red state and could factor into the fight for U.S. Senate control.

Allred, a three-term congressman from Dallas, was in an uphill battle against Cruz, who has urged Republicans to take the race seriously after only narrowly winning his last reelection in 2018. No Democrat has won statewide office in Texas in 30 years, the longest political losing streak of its kind in the U.S.

But shifting demographics in Texas — driven by a booming Hispanic population — and shrinking margins of victory for GOP candidates have sustained Democrats' belief that victories are in reach. Those hopes left Democrats seeing Texas as one of their few pickup opportunities in a year when they were defending twice as many Senate seats as Republicans nationally.

Both candidates raised more than $160 million combined in the race.

Allred, who would become Texas' first Black senator, has powered his upset bid by presenting himself as a moderate choice while mostly keeping political distance from Vice President Kamala Harris. That has not deterred Cruz from casting his opponent as politically likeminded with Harris, whose presidential campaign has not made an aggressive play to flip Texas.

Allred, 41, is a former NFL linebacker and civil rights attorney who has made abortion rights one of his top issues in a state that has one of the nation's most-restrictive bans. He campaigned with Texas women who were hospitalized with serious pregnancy complications after the Texas ban took effect and has vowed to help restore the landmark Roe v. Wade decision that guaranteed a woman's constitutional right to abortion.

Cruz, who is seeking a third six-year term, has largely avoided the topic on the campaign trail while hammering Allred on the issues of immigration and policies that support transgender rights. He has called Allred out of touch with Texas, where Democrats control the state's big cities but have been shut out of power statewide and at the Texas Capitol, where the GOP holds commanding majorities.

Allred hopes to take advantage of Texas' shifting demographics, which along with the booming Hispanic population also includes an increase in the number of Black residents and people relocating from other states. He also has experience defeating a high-profile Republican incumbent, having entered Congress with a victory over Rep. Pete Sessions, who later successfully ran in a different district.

In the late stages of the race, Allred sought to tap into some of the Democratic enthusiasm around Harris at the top of the ticket, including appearing at a packed Houston rally with the vice president and superstar Beyoncé. Cruz spent the final week of the race rallying supporters in solidly GOP rural and suburban counties that have been key firewalls to Democratic gains in Texas.