Nov 1 - As Americans head to the polls on Tuesday for midterm elections, lists the Trump administration has compiled of possible noncitizen voters could be used to contest the validity of the results.

With US President Donald Trump’s Republican Party fighting to maintain control of Congress, here’s how the lists could affect the midterms. WHAT HAS THE TRUMP ADMINISTRATION SAID ABOUT THE LISTS?

The Trump administration has acknowledged sending letters to election officials in five states — California, Washington, New Jersey, Pennsylvania and Nevada — as of October 30, saying it identified noncitizens on their voter rolls, according to a Justice Department document seen by Reuters.

In an October 13 letter, the Justice Department demanded California not count ballots from about 20,000 registered voters "who federal agencies reasonably believe are likely noncitizens" without first verifying their citizenship, warning that election workers who processed them could face prosecution. Trump endorsed the warning on social media: “They will all go to jail for a long period of time!!!”State officials rebuffed requests to set aside ballots of people on the lists, which have not been made public.

The Justice Department is now suing California to block the state from counting any ballots from the list of 20,000 voters. California says its safeguards against noncitizen voting are robust.

Noncitizen voting is illegal and can lead to jail time, fines and deportation. The White House says noncitizen voting is a significant problem requiring aggressive enforcement to protect election integrity. Trump has long alleged it is widespread, but available evidence indicates it is exceedingly rare. A Reuters investigation in July found just 129 cases in which noncitizens were federally charged with voting illegally since a federal “voting by aliens” statute was created by Congress in 1996; many appeared to stem from confusion or administrative errors rather than intentional fraud.

The Justice Department has since ramped up noncitizens voting prosecutions. “Close elections are not rare, and every illegal ballot cancels out the vote of an American citizen,” a Justice Department spokesperson, Kiersten Pels, said in a statement. Homeland Security Secretary Markwayne Mullin claimed without evidence in a Fox News interview on Saturday that his agency had found 300,000 noncitizens on the voter rolls. HOW DID THE TRUMP ADMINISTRATION COMPILE THE LISTS?

The federal government has no centralized list of US citizens who are registered or eligible to vote. But the Trump administration has aggressively sought state voter data to expand its role in determining voter eligibility.

States have constitutional authority over federal elections and many states make voter rolls public with private information, such as driver’s license numbers and the last four digits of Social Security numbers, redacted.

The administration has sought unredacted rolls to identify alleged noncitizens. At least 16 states, including Alabama and Texas, have complied voluntarily. Thirty states, including California and New York, as well as Washington, D.C., have not complied and have been sued by the administration for their voter rolls. Courts have rejected 27 of those efforts so far, with many judges finding the federal government has no role in determining voter eligibility.

The Justice Department has appealed many of those losses. “Voters have a right to accurate voter rolls, and states shouldn’t be hiding them from federal review,” said Pels, the department’s spokesperson.

The Department of Homeland Security obtained at least partial voter-roll data from at least 47 states, typically including names, addresses and registration status and, in some cases, additional information such as dates of birth, according to a recent internal DHS email reviewed by Reuters. Federal investigators then matched the voter data against government databases to identify potential noncitizens, the email shows.

DHS did not respond to a request for comment. It has said its investigations are conducted professionally and lawfully to safeguard election integrity. WILL THE LISTS IMPACT THE MIDTERMS?

The lists could provide a basis for challenging close election results, even if the administration struggles to prevail in court. Under most state laws, only candidates or voters can challenge election results, but a losing candidate could argue that suspected noncitizen votes made it impossible to determine the rightful winner, three legal experts told Reuters. And the Justice Department could pursue other legal avenues to try to block certification of victors. The Justice Department has said it will enforce the law wherever the evidence leads.

Such challenges would face significant legal hurdles, partly because reviews of the administration’s lists of potential noncitizen voters have found that many people on the lists are US citizens.

On October 28, a federal judge in California rejected the Justice Department's bid to block ballots from 20,000 voters it identified as likely noncitizens, saying the move would "wreak havoc" on the November 3 elections and questioning the reliability of the list. A federal appeals court upheld the ruling on October 30, citing a “material risk” of disenfranchising eligible voters.

The Justice Department would “probably” appeal to the US Supreme Court, acting US Deputy Attorney General Trent McCotter said on Fox News on Saturday. He has acknowledged the California list could include US citizens.

The lists and resulting challenges could cast doubt on narrow Democratic victories and prompt Trump-aligned state officials to seek further review or try to delay certification, though such efforts would face formidable obstacles, the legal experts said. The administration says its efforts are aimed at identifying and prosecuting illegal voting and protecting election integrity.