Democratic Senator Elizabeth Warren of Massachusetts has ruled out a presidential run in 2016. Warren had recently been the subject of growing speculation as a potential progressive challenger to Hillary Clinton, who is widely expected to seek the Democratic nomination. Warren has generated a wide following as a vocal proponent of Wall Street regulation and the key figure behind the Consumer Financial Protection Bureau. But speaking to reporters on Wednesday, Warren vowed to serve out the remainder of her Senate term, through 2018. Supporters of a Warren candidacy note then-Senator Obama made the same pledge before changing his mind to run in 2008.