Radio ads and direct mail funded by Priorities will go on the air and into mailboxes in Ohio, Illinois, Arizona and Florida, focusing in particular on turning out Latino and African-American voters in support of Clinton. Priorities plans to spend a total $4.5 million to boost voter turnout in the March states, building on spending that began in February.

The expenditures are a tacit recognition of Bernie Sanders’ enduring strength in the primary; Sanders has posed a greater challenge to Clinton in the nomination than her allies expected. The super PAC bought radio time supporting Clinton ahead of Michigan’s hard-fought primary on Tuesday, which Clinton narrowly lost.

But beyond the primary, Priorities’ spending also could position Clinton better in a general election against a Republican, assuming she wins the nomination, by energizing Democrats and countering Republican spending against her.

“This allows us to continue making investments in primary states to ensure Hillary Clinton enters the general election in the strongest possible position,” said Guy Cecil, co-chairman of Priorities, in an open memo published March 2. “The coming onslaught from Republican outside groups makes our work crucial to a Hillary Clinton victory.”

The super PAC’s increased involvement in the Democratic primary began shortly after Sanders’ landslide victory in New Hampshire. Priorities has already spent $4.2 million since the beginning of February, according to FEC filings, going through $1.3 million on direct mail and more than $2.9 million on radio ads in states like South Carolina, Georgia and Texas.

Tad Devine, top strategist for the Sanders campaign, warned last week that the spending would hurt Clinton’s image in primary states. Some Sanders staffers have discussed pushing at the Democratic convention for a commitment from Democrats not to spend money super PAC money in any future presidential or congressional primaries. “Priorities is spending millions,” Devine said last week. “As this starts coming more into focus, people are going to get very motivated” to come out for Sanders.

Priorities, however, is not the only super PAC spending money in the Democratic primary. National Nurses United for Patient Protection, a super PAC affiliated with a nurses’ union that has endorsed Sanders, has spent $1.9 million supporting the Vermont senator, including with billboards, canvassing and radio buys.

As the campaign has ramped up, fundraising for Priorities has steadily increased since last year. The super PAC raised $10 million in January, compared with $16 million in the first six months of last year.

This article was originally published on Time.com.