Jackson's campaign said his political transformation stands in contrast with Collins. He joined the Democratic Party in 2004 and continued rising politically, winning a state Senate seat four years later. - Joe Raedle/Getty ImagesJackson's political ascent continued in 2018 when Democrats captured the majority in the Maine Senate and picked him as their leader. Advertisement AdvertisementStewart, the Maine Senate Republican leader, had nothing positive to say about Jackson's tenure. Advertisement AdvertisementOne thing that did stand out from Jackson's campaign, though, was how closely he tied himself to Platner.