Donna Miller defeats Jesse Jackson Jr. in Illinois 2nd District primary

Donna Miller has won the Democratic primary for Illinois' 2nd District, a seat held by Rep. Robin Kelly, who is running for U.S. Senate.

The latest: Miller defeated former Rep. Jesse Jackson Jr., who was seeking a return to the seat after serving a federal sentence for campaign finance fraud.

Why it matters: The race is one of several Democratic primaries in which millions of dollars in outside PAC spending may have helped shape the outcome.

By the numbers: Miller received over 40% of the vote to Jackson's 28% when the Associated Press called the race.

Zoom in: Miller is a Cook County Board commissioner representing the 6th District and has spent decades working in health care. She previously served as board chair of Planned Parenthood of Illinois.

• She also ran for state Senate in 2012, losing in the 15th District.

Zoom out: The district spans large swaths of the South Side of Chicago and the south suburbs, extending down to Peoria.

• The heavily Democratic district means the primary often decides the seat.

Between the lines: The 2nd District represents one of several races that drew millions in outside PAC spending.

• In February alone, Miller benefited from $2.4 million in ads linked to the American Israel Public Affairs Committee (AIPAC), while one of her opponents, Robert Peters, was hit with $735,000 in attack ads from the crypto industry-linked Fairshake PAC.

The intrigue: Miller's win shuts down a high-profile comeback attempt by Jackson, once one of Chicago's most prominent political figures.

What's next: In November, Miller will face Republican challenger Mike Noak for a seat that has been held by a Democrat since 1953.