Former President Trump often claims that big waves of immigrants who aren't U.S. citizens are voting in our elections — and influencing outcomes — with Democrats' blessing. They're not.

Why it matters: There's no evidence such voting has ever happened on any significant scale. But the conspiracy theories live on, fueled by Trump, Elon Musk and others who keep injecting hard-to-imagine scenarios into the debate over border security.

• "They are allowing these people to come in ... they are signing them up to vote," Trump told a crowd at a campaign stop in Iowa in January.
• "That's why you are having millions of people pour into our country, and it could very well affect the next election."

Reality check: Non-citizen immigrants are barred by law from voting in federal elections. The very few who try it typically do so by accident, and are caught. The penalties can be severe, and include prison time or deportation.

• Voting as a non-U.S. citizen "is a federal crime ... a removable offense, meaning that you can be deported," Sean Morales-Doyle, director of the Brennan Center Voting Rights Program, told Axios.
• "The stakes are really, really high. And it's really easy to figure out that you did it," Morales-Doyle said.

Undocumented immigrants in particular are widely known to steer clear of giving out personal information or registering for anything involving U.S. and state governments, out fear of facing arrest or deportation.

• Some have even avoided public services they're entitled to, such as food stamps or housing benefits.

Between the lines: It's theoretically possible for a foreigner to first lie about their citizenship status to register to vote, and then commit a federal crime by voting.

• Voters typically are required to provide some kind of proof of identity to register to vote, such as a driver's license.
• Not all of those ID methods require citizenship, but voter registration and voting records are both recorded, making it easy to catch non-citizens at various points in the voting process.
• States are required to regularly vet and update voter rolls, to look for anyone who isn't eligible.
• Many states have passed additional measures aimed at ensuring voters are U.S. citizens.

When non-citizens have ended up on voter rolls it's often by accident — not part of any conspiracy to affect an election, Morales-Doyle said.

• There have been several cases in which DMV officials have mistakenly led non-citizens to register to vote under "motor voter" policies.

Zoom in: Republicans seeking to justify claims of illegal voting by immigrants point to a few reports and probes that purported to have found large numbers of non-citizens who registered to vote or voted. Those claims wilted under scrutiny.

• In 2019, Texas began investigating what GOP officials claimed were as many as 100,000 non-citizens on the state's voter rolls.
• The alleged number of illegal registrants ticked down as the claims were examined. The investigation fizzled, and eventually a federal judge killed the probe, saying it was infringing on eligible voters' rights.
• On the heels of Trump's first campaign for president in 2016, the Brennan Center for Justice examined about 23.5 million votes in 42 jurisdictions, looking for evidence of the illegal voting by non-citizens that Trump had claimed was prevalent.
• It found about 30 suspected illegal votes.

Even so, Trump's claims about illegal voting have undermined confidence in elections, mainly among Republicans.

• In 2016 he claimed — without evidence — that he lost the popular vote to Hillary Clinton by 2.8 million votes because 3 million undocumented immigrants had voted.
• In 2020, he blamed his close losses to Joe Biden in several key states on thousands of illegal votes. His team lost dozens of court cases trying to prove it.
• Now Trump controls the Republican National Committee — whose new leaders are asking prospective hires whether they believe Biden was legitimately elected in 2020.

What to watch: Some municipalities have enabled non-citizens to vote in local elections — including in California, Maryland, Vermont and Washington, D.C.

• Those voter rolls are separate from the national voter registration process, and don't allow non-citizens to also vote in state or federal elections, Morales-Doyle said.