She will now face Republican Allan Fung, mayor of the state's second largest city, who came in 4.5 points behind Raimondo in a three-way race in 2014.
Wednesday's primary winners will have to contend with another three-way contest Nov. 6, with former Republican lawmaker Joe Trillo, who chaired President Donald Trump's 2016 campaign in Rhode Island, running as an independent.
Rhode Island also selected nominees for U.S. Senate, U.S. House, lieutenant governor and other offices in the rare Wednesday vote. About 145,000 people cast ballots, or nearly 20 percent of voters, according to the state Board of Elections. The turnout in recent midterm primaries has hovered around 20 percent.
In the campaign, Raimondo cited a falling unemployment rate in the state, as well as new job training programs and free community college tuition started during her tenure.
She defeated Matt Brown, a former Rhode Island secretary of state. Brown, who last held office over a decade ago, pushed himself as the grassroots alternative and hammered Raimondo for her close corporate ties.
Raimondo raised $7.7 million, 20 times Brown's total. She took aim at Fung in her victory speech, saying he won't stand up to Trump and he opposes her administration's job creation policies. Her supporters chanted "four more years."
Malcolm Griggs headed to the polls in Warwick to vote in the Democratic primary for Raimondo, who he feels has done a good job helping the state's economy, attracting businesses and augmenting businesses already in Rhode Island.
"She put people to work and that matters," said Griggs, 58, who works in the banking industry.
On the Republican side, Fung, the mayor of Cranston, defeated Patricia Morgan, who leads the tiny House minority caucus in the overwhelmingly Democratic General Assembly.
Fung tried to keep a low profile in the primary, putting out few detailed policy proposals, dodging questions about where he stands on various issues and agreeing to just one debate on a small radio station with limited reach. Raimondo also did not participate in debates.
Fung said his victory is a sign that Rhode Islanders are ready to take back the state from insiders and "big shots" and reject the status quo. He said he's ready to "lead this revolution."
In congressional races, Democratic Sen. Sheldon Whitehouse and Rep. David Cicilline easily won their primaries. Rep. Jim Langevin was unopposed in the Democratic primary.
The 62-year-old Whitehouse is a leading voice in the Senate pushing to do more to address climate change. He has also been critical of Trump on a number of issues, including by pushing to protect special counsel Robert Mueller's Russia investigation.
The most closely watched down-ticket race was for lieutenant governor. Incumbent Democrat Dan McKee narrowly beat self-described progressive state lawmaker Aaron Regunberg. The position has few official duties, but officeholders have used it as a way to advance certain causes on a statewide level. McKee wants to expand the position's powers.
McKee campaigned on his experience as the incumbent and a former six-term mayor. The 67-year-old politician painted Regunberg as too inexperienced. Regunberg, 28, had wanted to use the office to advocate for reform at the Statehouse.
Former U.S. Attorney Peter Neronha was unopposed for the Democratic nomination for Rhode Island attorney general, virtually guaranteeing him the job. Republicans didn't put forward a candidate and Neronha faces no significant opposition in November.
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