January 2016: Despite getting pushed out by the Obama administration, Flynn has his security clearance renewed.
February 2016: Flynn begins serving as an adviser for the Trump campaign and will soon become one of its public fixtures. He will even be considered as a potential running mate. Speaking at the Republican National Convention in July, Flynn leads the crowd in anti-Hillary Clinton "Lock her up" chants and says in his speech, "If I did a tenth of what she did, I'd be in jail today."
https://www.nydailynews.com/news/politics/timeline-michael-flynn-obama-trump-troubles-article-1.3147873