WASHINGTON — State officials who run U.S. elections are braced for possible intervention by President Donald Trump's administration in Tuesday's midterms -- fearing federal authorities could disrupt voting, challenge ballot counts or try to block unfavorable results. Trump, whose Republicans face an uphill battle to keep control of Congress, has repeatedly questioned the integrity of U.S. elections and urged his party to "nationalize" voting in at least 15 places. The White House says it is protecting election security, and many of the feared scenarios remain hypothetical. The U.S. Constitution gives the president no direct role in running elections, and courts have so far rebuffed the administration's main legal challenges. Here are the key potential flashpoints: Who gets to vote The Justice Department has sued 30 states and the District of Columbia to obtain their voter registration lists, saying it needs them to find non-citizens. It has lost more than two dozen of those cases. It has also demanded that ballots be set aside from about 20,000 people in California and more than 400 in Wa