In February, ahead of the Texas statewide primary, Carlos Vanegas at the Harris County Elections Office in Houston pushes a cart with mail-in ballots to be sent to voters. The county ultimately rejected thousands of the mail ballots it received back.

In February, ahead of the Texas statewide primary, Carlos Vanegas at the Harris County Elections Office in Houston pushes a cart with mail-in ballots to be sent to voters. The county ultimately rejected thousands of the mail ballots it received back. / Scott Dalton for NPR

A total of 24,636 mail-in ballots were rejected throughout Texas in the March 1 primary election, the Texas secretary of state's office said Wednesday.

That's a 12.38% rejection rate — far higher than in previous contests.

Local election officials, as well as voting rights advocates, have said many voters were tripped up by a GOP-backed law that went into effect late last year.

James Slattery, a senior state attorney at the Texas Civil Rights Project, says these final figures show Texas' new voting law, known as Senate Bill 1, was "catastrophic for democracy" in the state.

"The rejection rate went up by a factor of 12 since the last election," he said. "The only reason that the rejection rate soared this high is that Senate Bill 1 imposed this new ID requirement and it is disenfranchising eligible voters."

Under SB 1, voters have to provide a partial Social Security number or driver's license number on their mail ballot application — as well as on the return envelope. The ID number they provide has to match what's on their voter registration record.

Many voters either completely missed the new ID portion of the return envelope or had mismatched IDs, local officials said.

Some county election officials reported that up to 40% of ballots that were returned were initially flagged for rejection. Eventually some voters were able to fix their ballots, but many voters were not.

Officials in Harris County — home to Houston, and the state's most populous county — had said they ultimately rejected 19% of the mail-in ballots they received.

According to state data, there was a slightly higher final rejection rate among ballots cast in the Democratic primary compared with the Republican primary.

The Texas secretary of state's office reported 12.87% of Democratic mail-in ballots cast were rejected during the primary, while 11.77% of Republican ballots were rejected. A total of 14,281 Democratic ballots were rejected, and 10,355 Republican ballots were rejected.

Sam Taylor, assistant secretary of state for communications, said in a statement last month that many of these issues can be addressed through voter education.

"While in years past we have focused our voter education efforts on in-person ID requirements," he said, "this year we are also devoting a significant portion of our voter education campaign to enhancing awareness of the new mail-in ballot ID requirements."

Slattery said he is skeptical that will be enough to address the issues created by SB 1.

"More voter education will help at the margins," Slattery said. "But it does not explain a 12-factor jump in rejections. It is inherent in the nature of the process."

Slattery said he is "very worried" rejection rates will "only be worse in November" for the general election, when more voters are expected to cast mail-in ballots.

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