The two announcements seemed certain to reignite partisan debates over the frequency and impact of voter fraud, which Republicans have claimed is rampant in America. Democrats scoff at that notion, and a voter fraud commission started by (and later angrily disbanded by) President Donald Trump found no evidence of widespread electoral fraud.

“Every single instance of illegal voting threatens democracy in our state and deprives individual Texans of their voice,” Paxton, a firebrand conservative who has prosecuted isolated cases of illegal voting with gusto, said in a statement.

But Democrats and voting rights advocates were skeptical of the state’s claims. More than 8.3 million people voted in the Texas governor’s race last year, which means that even if all 58,000 people who voted were, in fact, found to be noncitizens and voted in 2018 — a claim that no state official has made — they would have amounted to only 0.69 percent of all votes cast.

“Because we have consistently seen Texas politicians conjure the specter of voter fraud as pretext to suppress legitimate votes, we are naturally skeptical,” Rep. Rafael Anchia, a Democrat in the Texas House of Representatives, said in a statement.

Kristen Clarke, the president of the Lawyers’ Committee for Civil Rights Under Law, also cautioned that the state’s findings, and the speed with which the attorney general raised the prospect of prosecution, could foreshadow an attempt at voter suppression.