WASHINGTON -

Debbie Dingell plans to run this year for the seat being vacated by her husband, Rep. John Dingell of Michigan, a Democratic strategist with knowledge of the lawmaker's thinking confirmed to CNN.

It is believed she will make the formal announcement Friday.

John Dingell, the longest serving member of Congress in history, announced Monday that he'll retire at the end of the year.

He has served in the House for 58 years. He was 29 when he was first elected in a special election to serve the remainder of his late father's term. John Dingell, Sr. had held the seat since its creation in 1932.

Read: Full statement from John Dingell on retirement

There was speculation that Debbie Dingell, the congressman's wife of 38 years and a longtime Democratic National Committee member, would run for her husband's seat.

The Democratic strategist told CNN that Mrs. Dingell's entry into the race would basically clear the field of other major Democrats.

Democrats dominate Michigan's 12th Congressional District, which includes several working class southern suburbs of Detroit known as the "Downriver" area. The district stretches west to include Ann Arbor, home to the University of Michigan.

Dingell grabbed 68% of the vote in his 2012 re-election. And Barack Obama won two-thirds of the vote in the district in the 2008 and 2012 presidential elections.

Dingell has been approached by multiple people in Michigan and Washington about a potential bid.

In addition to her 30-year career at General Motors as a senior executive, Dingell has served on multiple boards of charities and organizations and has chaired several political campaigns, including former Vice President Al Gore's presidential campaign in Michigan.