Hillary Clinton is shown after a community meeting at the House of Prayer Missionary Church in Flint, Mich., on Sunday. (Jeff Kowalsky/Bloomberg)

The main super PAC supporting Democratic presidential hopeful Hillary Clinton is making its first significant foray into the 2016 primary, launching a radio campaign in South Carolina and spearheading a $4.5 million effort to drive early turnout of African American, Latino and female voters in states that hold contests in March.

The early engagement by Priorities USA Action — which originally planned to hold its fire for the general election — marks the first major infusion of super-PAC money on Clinton’s behalf and underscores how crucial South Carolina has become in her battle with Sen. Bernie Sanders of Vermont.

The Priorities group is rolling out the early vote campaign Friday in partnership with the League of Conservation Voters, an environmental advocacy organization, and EMILY’s List, which works to elect Democratic women.

Separately, Priorities USA is spending $500,000 to launch the radio ad in South Carolina beginning Friday, casting Clinton as the candidate to build on President Obama’s legacy.

The burst of activity serves as an acknowledgment of the tough fight Clinton finds herself in against Sanders, who trounced her by more than 20 points in New Hampshire Tuesday. It also could provide fresh ammunition for Sanders, who has repeatedly castigated the former secretary of state for being supported by two big-money super PACs.

During Thursday night’s PBS debate in Milwaukee, Clinton attempted to distance herself from Priorities USA and the donations it has received from Wall Street players, noting the group was first started to support Obama’s reelection. “It’s not my PAC,” she said.

Guy Cecil, chief strategist for Priorities USA, said the new ads will solely focus on positive messages about Clinton. He described the early vote campaign as an effort that will also pay dividends this fall if she is the Democratic nominee.

“We have always seen as our primary responsibility the general election, making sure that Hillary wins, and we have always thought we would assess where we were, to make sure we were doing everything possible to build a long-term coalition for her campaign,” Cecil said.

“It’s very clear for us that both in the primary and the general election, women, African American and Latino voters are an important part of the Clinton coalition,” he said.

The effort kicks off in Georgia, where early voting began Monday. Starting Friday, voters are being targeted across a variety of mediums — in the mail, on the radio and online — with ads that seek to tie Clinton tightly to Obama. One banner ad features a photo of them standing together, beaming.

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The campaign is set to roll out in more than two dozen states that hold primary contests in March, with a heavy presence in those where people can vote early in person: Arkansas, Oklahoma, Tennessee, Texas, Louisiana, Florida, Illinois, North Carolina, Ohio and Arizona.

Digital ads will be “geocoded,” allowing viewers to click on them to get the location of their early vote location.

“One of the things that has happened in last five to six years is that Republicans have engaged in all-out assault on voting rights,” Cecil said. “We want to make sure we are educating voters on where they can vote, how they can vote and when they can vote, and this was a great way to do that.”

The program will amplify the on-the-ground organizing that the Clinton campaign has been undertaking in March states over the past several months. On Saturday, her husband, former president Bill Clinton, is scheduled to headline an early-vote organizing event at a high school in Atlanta.

Her advisers have made it clear that turning out African Americans and Latinos in large numbers is vital.

“For Hillary Clinton and her campaign, the March states represent an opportunity to build a coalition of support that’s as diverse as the Democratic Party itself,” campaign manager Robby Mook wrote in a memo released Tuesday. “Hispanics and African Americans play a critical role in who we are as a party and who we are as a nation. Many of the most delegate-rich states also have some of the largest minority and urban populations — states like Texas, Georgia, Alabama, Illinois and Florida.”

Meanwhile, in South Carolina, Priorities USA is aiming to mobilize black voters to come out for Clinton with its new radio ad, which is set to remain on the air until the Feb. 27 primary. The spot was produced by FUSE Advertising, an African American media firm based in St. Louis.

“We all worked hard in 2008 and 2012 to elect President Obama,” the commercial begins. “And we’ve seen with our own eyes how Republicans have tried to tear him down every step of the way. We can’t let them hold us back. We need a president who will build on all that President Obama has done. President Obama trusted Hillary Clinton to be America’s secretary of state. And we know Hillary Clinton has the vision and courage to help build an economy to support our communities.”

“Hillary Clinton will always stand strong for us,” the ad concludes.

The campaigns by Priorities USA mark a major ramp-up for the super PAC, which until now had spent less than $500,000 to produce one TV commercial and a collection of digital ads defending Clinton against GOP attacks and swiping at Republicans such as Donald Trump and Jeb Bush.

The group still has a substantial cash reserve, thanks to seven-figure contributions from labor unions and from wealthy donors, including billionaire investor George Soros, hedge fund manager S. Donald Sussman and entertainment executive Haim Saban. At the end of January, the super PAC had nearly $45 million in the bank and another $42 million in commitments.

Priorities’s focus on mobilizing African Americans and Latinos comes as Cecil and other top Democrats are launching a separate nonprofit with similar aims. The group, called Every Citizen Counts, has raised $25 million to boost voter registration and challenge Republican-backed state laws limiting early voting and same-day registration.

It was set up in July by Democratic lawyer Marc Elias, who also serves as general counsel for Clinton’s campaign. As a tax-exempt “social welfare” organization, Every Citizen Counts can accept unlimited donations from individuals and corporations, without disclosing its donors.

Cecil said the organization has no connection to the super PAC and will not get involved in the Democratic primary.

Alice Crites contributed to this report.