Barry Lee Myers, whose nomination by President Trump to lead the National Oceanic and Atmospheric Administration remained unconfirmed by the Senate for more than two years, asked the White House this week to withdraw it, saying that surgery and chemotherapy made it “impractical” for him to serve.

Mr. Myers, the former chief executive of AccuWeather, a private forecasting company that relies largely on data from NOAA, was first nominated by Mr. Trump in 2017. But the nomination stalled in the Senate, leaving NOAA without a Senate-confirmed leader for the longest period since the agency was created in 1970.

Democrats had argued that Mr. Myers’s ties to AccuWeather would be a conflict of interest. Mr. Myers stepped down as chief executive in January 2019, but the company, founded by his brother, is still family-run. Mr. Myers’s brother is the current chief executive.

Democrats also criticized Mr. Myers’s previous eagerness to privatize NOAA’s National Weather Service and to fight government programs that would compete with AccuWeather services.