Only U.S. citizens are eligible to vote in this fall's election for president and other top offices. While that's nothing new, the potential for noncitizens to register or vote has been receiving a lot of attention lately.

Citing an influx of immigrants in recent years at the U.S.-Mexico border, Republicans have raised concerns about the possibility that noncitizens will be voting — something that has rarely occurred in the past. In Congress, House Speaker Mike Johnson is seeking to link an extension of federal government spending authority to a proposal requiring states to obtain proof of citizenship when registering people to vote.

In various states, GOP officials have launched reviews of voter rolls, issued executive orders and placed constitutional amendments on state ballots as part of an emphasis on thwarting noncitizen voting. Some Democrats contend the measures could create hurdles for legal voters, are unnecessary and lead people to believe the problem of noncitizens voting is bigger than it really is.

People cast their ballots Nov. 3, 2020, at the National World War I museum in Kansas City, Mo. Some Republican lawmakers are taking extra steps to prevent noncitizens from voting over their concerns that illegal border crossings could lead to voter fraud.

A 1996 U.S. law makes it illegal for noncitizens to vote in elections for president or members of Congress. Violators can be fined and imprisoned for up to a year. They can also be deported.

When people register to vote, they confirm under penalty of perjury that they are U.S. citizens. Federal law requires states to regularly maintain their voter rolls and remove anyone who is ineligible, a process that could identify immigrants living in the country illegally.

No state constitutions explicitly allow noncitizens to vote, and many states have laws that prohibit noncitizens from voting for state offices such as governor or attorney general. But some municipalities in California, Maryland and Vermont, as well as the District of Columbia, do allow voting by noncitizens in some local elections such as for school board and city council.

Congress needs to approve a stopgap spending bill before the Sept. 30 end of the budget year to avoid a government shutdown. At the urging of some Republicans, Johnson is seeking to combine a six-month extension of government spending with a measure requiring proof of citizenship, such as a birth certificate or passport, to register to vote.

Johnson, who said Congress has a responsibility to "ensure that only American citizens can decide American elections," has put off a vote on the measure for now because it doesn't have enough support to pass. But Johnson is signaling he's not backing off linking the two main pillars of the bill.

The plan is similar to a bill Republicans pushed earlier this year known as the Safeguard American Voter Eligibility Act. That legislation passed the Republican-led House in July largely along partisan lines but has not come to a vote in the Democratic-led Senate.

House Democratic Leader Hakeem Jeffries said that he opposes the latest Republican attempt to require proof of citizenship for voter registration. He said the stopgap spending bill should be free of "partisan policy changes."

The Biden administration also has opposed the Republican efforts while asserting that existing laws against noncitizen voting are working.

Luis Gil, a Republican candidate for Franklin County commissioner in central Ohio, speaks in favor of a constitutional amendment that would prohibit noncitizen voting Oct. 6, 2022, at the Ohio Statehouse in Columbus, Ohio. Ohio is one of several states that passed such amendments between 2018 and 2022.

Data from states indicates that voting by noncitizens is rare.  But Republican officials have highlighted voter registration reviews that turned up potential noncitizens.

Texas Gov. Greg Abbott, a Republican, said last month that more than 6,500 potential noncitizens have been removed from Texas voter rolls since 2021, including 1,930 with "a voter history" who have been referred for investigation by the attorney general's office. Texas has almost 18 million registered voters.

Ohio Secretary of State Frank LaRose, a Republican, said in August that he referred for potential prosecution 138 apparent noncitizens found to have voted in a recent election and 459 more who registered but did not vote. Those figures were higher than reviews from previous years but a small fraction of the more than 8 million registered voters in Ohio.

Alabama Secretary of State Wes Allen, a Republican, recently announced that 3,251 people previously identified as noncitizens by the federal government are being switched to inactive status on the state's voter registration rolls. They will be required to provide proof of citizenship and fill out a form to vote this fall. Alabama has more than 3 million registered voters.

In Georgia, Republican Secretary of State Brad Raffensperger found that 1,634 potential noncitizens tried to register to vote between 1997 and 2022, though election officials flagged them and none was registered. Georgia registered millions of other voters during that time.

Some election administration experts have said the voter roll reviews show that current tools to flag noncitizen voters are working.

Speaker of the House Mike Johnson, R-La., speaks as Republican presidential candidate former President Donald Trump listens during a news conference April 12 at Mar-a-Lago in Palm Beach, Fla.

Arizona provides a case study for the long-running attempts by Republicans to prohibit noncitizen voting.

Under a 2004 voter-approved initiative, Arizona required a driver's license, birth certificate, passport or other similar document to approve a federal voter registration application. But the U.S. Supreme Court ruled in 2013 that Arizona cannot require documentary proof of citizenship for people to vote in federal elections.

The state responded by creating two classes of voters. For state and local elections, voters must provide proof of citizenship when they register or have it on file with the state. But because that cannot be required in presidential and congressional elections, tens of thousands of voters who have not provided proof of citizenship are registered only for federal elections.

An August order by a divided U.S. Supreme Court will allow voter registration forms submitted without "documentary proof of citizenship" to be rejected by Arizona counties while litigation over the law continues. People will be able to register to vote in presidential and congressional elections using a different federal form that requires people to swear they are citizens under penalty of perjury, without requiring proof.

Republican-led legislatures in eight states have proposed constitutional amendments on their November ballots declaring that only citizens can vote.

Proposals in Iowa, Missouri, North Carolina, Oklahoma, South Carolina and Wisconsin would replace existing constitutional provisions stating that "every" citizen or "all" citizens can vote with new wording saying "only" citizens can vote. Supporters contend the current wording does not necessarily bar noncitizens from voting.

In Idaho and Kentucky, the proposed amendments would explicitly state: "No person who is not a citizen of the United States" can vote. Similar wording won approval from Louisiana voters two years ago.

Voters in North Dakota, Colorado, Alabama, Florida and Ohio passed amendments between 2018 and 2022 restricting voting to "only" citizens.

Signs direct voters to the Minneapolis Elections and Voter Services center on Sept. 23, 2022, in Minneapolis.

Although noncitizen voting already is prohibited in the state constitution, Republican Gov. Jeff Landry of Louisiana is continuing to draw attention to the issue. He recently signed an executive order requiring state agencies that provide voter registration forms to include a written disclaimer that noncitizens are prohibited from voting.

In Georgia, Raffensperger is requiring every polling place to post a sign in English and Spanish warning noncitizens that it is illegal to vote.

Republican Attorney General Ken Paxton of Texas, citing "significant growth of the noncitizen population" in the state, set up a special email account to report suspected violations of election laws.

In Wisconsin, Republicans have filed a pair of similar lawsuits in recent weeks that challenge the state's process for verifying whether a registered voter is a citizen. The lawsuits seek court orders requiring the elections commission to perform checks to ensure there are no registered voters who are noncitizens.

North Carolina Republicans have sued the state election board, alleging it is not enforcing a new law aimed at removing people from voter rolls who seek jury duty exclusions because they are not citizens.

Tennessee's top election office sent letters in June asking for proof of citizenship from more than 14,000 registered voters, though those who failed to respond won't be barred from voting. The list was based on data from the state Department of Safety and Homeland Security, which has information about whether residents were U.S. citizens when they first interacted with that department.