Donald Trump’s campaign has alleged that polling station “anomalies” took place during early voting in the Las Vegas area last week.
A lawsuit filed in a Nevada court asks that records from four early voting spots that allegedly stayed open too late last Friday be impounded and preserved.
Long lines kept polls open past the 7pm posted closing time at locations that included a Mexican market and several shopping centres.
Officials say at one site, the last voter cast a ballot after 10pm.
Criticism is also coming from state Republican Party chief Michael McDonald.
But Democrat Hillary Clinton’s campaign dismissed the Nevada case in a Twitter message, calling it “a frivolous lawsuit”.