WASHINGTON — Longtime Trump confidant Roger Stone lost his bid for a new trial on Thursday after alleging bias and misconduct from a juror, closing a controversial chapter in the last case brought in special counsel Robert Mueller’s investigation into Russian activity in the 2016 election.

Stone was sentenced earlier this year to more than three years in prison for lying to Congress, witness tampering and obstruction of an investigation, but had sought a new trial after finding social-media posts critical of Trump from the jury forewoman.