WASHINGTON - US Senator Barbara Boxer, a California Democrat, said on Thursday she will not seek re-election in 2016. Boxer has served in the Senate since 1993 and was in the US House of Representatives for a decade before that. She has been a leading liberal voice for environmental protections and former chair of the panel that handles such issues. In a video posted on her website, Boxer said that, while she will not seek re-election, she is 'never going to retire.' Boxer will focus on electing a Democrat to fill the congressional seat and helping the Democratic presidential nominee in the 2016 election, according to the video.