NEW YORK (Reuters) - The race to succeed Republican New Jersey Governor Chris Christie got under way this week when a former Goldman Sachs executive entered the ring as the first Democratic contender to succeed Christie, whose popularity has slumped. Phil Murphy, a former Goldman Sachs executive and U.S. ambassador to Germany who has never held elected office, is seeking the Democratic nomination for the gubernatorial  election in November 2017.  Christie, who is not eligible to run for a third term, won the governorship in 2009, when he beat one-term Democrat Jon Corzine, also formerly of Goldman Sachs Group Inc. Murphy, who served as U.S. ambassador to Germany until 2013, said he would focus on issues such as equal pay for women and a higher minimum wage - legislative initiatives that Christie has either already vetoed and is expected to veto.  “It’s time for a governor who has your back. I will,” promised Murphy, 58, in a campaign ad released on Monday. He is a married father of four who lives in Middletown and retired in 2006 after 23 years at the Wall Street investment bank. Political observers say other possible candidates include Democrats such as state Senate President Stephen Sweeney and Jersey City Mayor Steven Fulop and Republicans such as Assembly Minority Leader Jon Bramnick, state Senate Minority Leader Tom Kean Jr and Lieutenant Governor Kim Guadagno. Christie has seen his approval ratings fall to fresh lows in recent weeks. He has been tarnished by the “Bridgegate” scandal and criticized as a no-show leader preoccupied first with his own presidential campaign and when that failed, with role as a top adviser to presumptive Republican nominee Donald Trump. “His approval ratings are terrible. They have been low and keep going down. He will leave unpopular,” said Julian Zelizer, a professor of political history at Princeton University. A poll of New Jersey voters last month showed 31 percent approve and 63 percent disapprove of Christie’s performance as governor, said John Weingart, associate director of the Eagleton Institute of Politics. Voters will likely seek a candidate very different from Christie, Zelizer said, particularly on transparency and righting the state’s finances.  “They are looking for someone who is antithetical to him. Someone they can trust, someone who is devoted to the state, and someone who seems clean and immune from scandal,” Zelizer said. “They want a governor who will bring in new kinds of industry and new pockets of growth.” 