One of the biggest super PACs supporting former President Donald J. Trump is adding $70 million to its television and digital reservations in the final six weeks of the campaign, including the first significant Republican super PAC ad buy in North Carolina since Labor Day.

The super PAC, MAGA Inc., is pouring the funds into four battleground states — North Carolina, Pennsylvania, Georgia and Arizona. The $70 million comes on top of $30 million in pre-existing ad buys by the group, for a total spending of $100 million in the final stage of the race.

Most of the group’s money is going into Pennsylvania, officials at the super PAC said. The former president’s advisers and allies believe that a Trump win in Pennsylvania would block Vice President Kamala Harris’s path to the White House.

But the spending in North Carolina reflects what has become a more competitive race there.

The super PAC plans to run crime-focused ads designed to portray Ms. Harris as a radical leftist, according to officials at the group. They will use examples of her record as a prosecutor in San Francisco to make the case that she is soft on crime. It’s a strategy Republicans have reliably used since the Nixon era.

Ms. Harris has been highlighting her record as a prosecutor, in part in an effort to blunt voters’ concerns about her being too liberal, according to two people with direct knowledge of her approach, who were not authorized to discuss the strategy publicly.

Trump allies have been anxious to prevent Ms. Harris from successfully distancing herself from her past liberal positions — particularly those she took as a presidential candidate in 2019 — and selling herself as the “change” candidate.