NEW YORK (Reuters) - New Jersey’s Republican lieutenant governor and a former investment banker running as a Democrat will head to a November face-off to succeed two-term Republican Governor Chris Christie, primary election results showed on Tuesday. The front-runner in the Democratic primary, former Goldman Sachs Group Inc executive and one-time diplomat Phil Murphy, declared victory about 90 minutes after polls closed. Unofficial results posted on NJSpotlight.com showed him with more than twice as many votes as his nearest rival, former U.S. Treasury Department official Jim Johnson, in a six-way race. “I humbly accept your nomination to be the Democratic candidate for governor of the great state of New Jersey,” Murphy said on Twitter.  Lieutenant Governor Kim Guadagno, the Republican favorite to succeed Christie, also held a strong lead over four rivals in her party’s primary, earning nearly half of the votes cast. Election results showed Guadagno with 47 percent of the Republican vote, followed by state Assemblyman Jack Ciattarelli in second place with 31 percent. The two primary victors will face off in the general election in November to succeed Christie, a once-rising Republican star whose popularity has plunged in recent years. New Jersey and Virginia are the only two states holding gubernatorial elections this year. Earlier indications were that voter interest in the New Jersey gubernatorial primaries was low.  Murphy, who served as U.S. ambassador to Germany under former President Barack Obama, significantly out-spent his opponents, loaning $15 million to his own campaign. He was also endorsed by former Vice President Joe Biden and the state’s Democratic Party. With Christie frequently out on the stump for Donald Trump during the 2016 presidential campaign, Guadagno has spent months as acting governor. But she has also had to distance herself from the unpopular Republican incumbent and has sparred with Ciattarelli over her plan to raise taxes on millionaires. While Christie was re-elected with 60 percent of the vote in 2013, his recent approval rating dropped to 20 percent following his frequent absences, the state’s 11 credit-rating downgrades and transportation problems.  Christie has also been tarnished by the scandal in which two former aides were convicted for scheming to close down lanes at the George Washington Bridge in 2013 to punish a mayor for failing to endorse Christie’s re-election campaign. 