Challenge From the Left: Bernie Sanders Is Running Formal announcement expected later this week By John Johnson, Newser Staff Posted Apr 28, 2015 5:53 PM CDT 168 comments Comments Sen. Bernie Sanders, I-Vt. in a photo from March of this year. (AP Photo/Pablo Martinez Monsivais, File) (Newser) – Hillary Clinton will have at least one challenger over her left shoulder for the Democratic nomination: Sen. Bernie Sanders, the Vermont independent who describes himself as a democratic socialist, will announce his candidacy on Thursday, reports Vermont Public Radio. The 73-year-old will focus on three main issues: income inequality, climate change, and campaign finance reform, a longtime adviser tells Politico. The plan is for a low-key announcement, followed by a splashier kickoff in Vermont in a few weeks, and then trips to the early-voting states. "Sanders' basic message will be that the middle class in America has been decimated in the past two decades while wealthy people and corporations have flourished," writes VPR. Expect him to press Clinton on where she stands on the Trans-Pacific Partnership, a proposed trade pact that he opposes as bad for working-class America. Sanders should have company soon in nudging Clinton leftward: Former Maryland Gov. Martin O'Malley is expected to join the race in May, reports Reuters.