WASHINGTON — K. T. McFarland, who was a deputy national security adviser in the Trump administration and then was picked to serve as ambassador to Singapore, withdrew her ambassadorial nomination on Friday after it had stalled in the Senate.
Ms. McFarland’s nomination had become embroiled in the controversy over the Trump campaign’s contacts with Russian officials, with some senators left wondering if she had answered questions deceptively when asked if she knew of discussions between Michael T. Flynn, the former national security adviser, and a Russian ambassador.
“Unfortunately, some Democrats chose to play politics rather than move forward with a qualified nominee for a critically important post,” President Trump said in a statement released Friday by the White House. “I wish K. T. the best as she uses her considerable wisdom and skill as a commentator to explain to the American people how to make American foreign policy great again.”
Senate Republicans could have approved her nomination unilaterally, but the fact that it was never brought to a vote suggested that she had made even some of them uneasy. Ms. McFarland was a member of the Trump transition team and then became Mr. Flynn’s deputy on the National Security Council, where she ruffled feathers with her intense partisanship.
In one meeting of the council, which sees itself as apolitical, she bragged to staff members that she was wearing shoes from Ivanka Trump’s brand. In another, she told the assembled career staff members, most of whom had been in the same roles during the Obama administration, that they needed to “make America great again.”
Mr. Flynn’s successor, Lt. Gen. H. R. McMaster, pushed Ms. McFarland out in an effort to return the council to a traditional professional operation. Her nomination as ambassador to Singapore was seen as an effort to reward her loyalty.
But in July, she was questioned in writing by Senator Cory Booker, Democrat of New Jersey, on whether she had ever spoken with Mr. Flynn, before Mr. Trump took office, about Mr. Flynn’s contacts with Sergey I. Kislyak, who was then the Russian ambassador to Washington. In her response to Mr. Booker, Ms. McFarland sidestepped an answer, writing, “I am not aware of any of the issues or events described above.”
When an email later surfaced showing that Ms. McFarland had been aware of a crucial Dec. 29, 2016, phone call between Mr. Flynn and Mr. Kislyak, questions were raised about her honesty. Mr. Flynn pleaded guilty last year to lying to F.B.I. agents about his interactions with Mr. Kislyak.
Ms. McFarland, who formerly served as a commentator on Fox News, has long been controversial. When she ran in 2006 for the United States Senate seat then held by Hillary Clinton, Ms. McFarland was found to have made multiple exaggerations about her résumé. Her opponent in the Republican primary race, John Spencer, routinely pointed out that Ms. McFarland had once claimed that helicopters were spying on her at Mrs. Clinton’s request. (Ms. McFarland said she was joking.