Some senior lawyers at Jones Day, one of the country’s largest law firms, are worried that it is advancing arguments that lack evidence and may be helping Mr. Trump and his allies undermine the integrity of American elections, according to interviews with nine partners and associates, who spoke on the condition of anonymity to protect their jobs.

At another large firm, Porter Wright Morris & Arthur, based in Columbus, Ohio, lawyers have held internal meetings to voice similar concerns about their firm’s election-related work for Mr. Trump and the Republican Party, according to people at the firm. At least one lawyer quit in protest…

On Friday evening, Justice Samuel A. Alito Jr. ordered election officials in Pennsylvania to keep late-arriving ballots separate and not to include them in announced vote tallies. (Pennsylvania’s secretary of state had already given the same guidance.)

Six Jones Day lawyers said that given the small number of late-arriving ballots involved in the litigation, and the fact that they already had been segregated, the main goal of the litigation seemed to be to erode public confidence in the election results.