CHICAGO (Reuters) - U.S. Congressman Dan Lipinski is campaigning for re-election in Illinois with a bullseye on his back, targeted not by Republicans but a coalition of progressive activists in his own Democratic Party on a mission to steer it further to the left.

U.S. Congressman Daniel Lipinski arrives at the Chicago Ridge Metra commuter train station before campaigning for re-election in Chicago Ridge, Illinois, U.S. January 25, 2018. Picture taken January 25, 2018. REUTERS/Kamil Krzacznski

Lipinski is among more than a dozen congressional Democrats facing credible challengers, mostly with progressive agendas, in nominating contests that will decide the party’s candidates for the November midterm elections.

Democrats need to pick up 24 seats from Republicans to take control of the U.S. House of Representatives. But first, they must contend with an energized left wing trying to define the party through the candidates on its ticket.

Lipinski’s Chicago-area seat is considered a safe win for Democrats in the fall. The incumbent’s fate in the March 20 primary will gauge enthusiasm among Democratic voters for the party’s moderates and few remaining conservatives.

“We are willing to hold our own people accountable, as well as our more consistent enemies,” said Sasha Bruce, senior vice president of campaigns and strategies at NARAL Pro-Choice America, which advocates for abortion and reproductive rights.

Groups such as NARAL, the Human Rights Campaign, which promotes gay rights, and Indivisible, a nationwide network which formed last year to resist Republican President Donald Trump, say Lipinski’s socially conservative views are out of touch with the district that first elected him in 2004.

“My values, the district and the nation are all in alignment,” opponent Marie Newman, 53, said over coffee at a bohemian cafe in the district, which extends from suburbs to Chicago’s South Side.

Lipinski, who opposes abortion and voted against the Democrats’ signature healthcare reform law, “is over there,” she added, picking up her purse and moving it to another table.

In a rare move against an incumbent, a half dozen national groups advancing leftist agendas on gay rights, workers’ rights and women’s issues mounted a $1 million independent campaign targeting Lipinski in mailers, television ads and online. They also have steered volunteers to canvass for Newman.

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The primary battle is a fresh display of Democratic tensions simmering since establishment politician Hillary Clinton beat U.S. Senator Bernie Sanders, an independent with socialist views often to her left, in a surprisingly close race for the party’s presidential nomination in 2016.

Sanders, who vowed to continue his fight, recently endorsed Newman in the Illinois contest.

Some liberal activists have discussed the need for new political tactics on the left that could rival the conservative Tea Party movement, which pushed the Republican agenda to the right with challenges to incumbents.

Lipinski, who inherited a heavily Polish and Irish district with a growing Latino population from his congressman father, said Democrats will pay a price if they drive away all but the most liberal views.

“It would be a disaster,” Lipinski, 51, said in a phone interview. “We need to make sure that we are a big-tent party.”

MAKING A POINT

Lipinski’s primary, one of the earliest this year, stands out due to the wide mobilization of progressive activists against an incumbent. Recent NARAL polling shows a tight race.

About a dozen other Democratic incumbents in the U.S. House face primary challenges from opponents with sufficient traction to have raised at least $50,000, the Campaign Finance Institute, a nonpartisan think tank, found in a review of federal campaign filings through the end of last year.

Contests remain fluid, with the candidate field still shaping up in some races. Most challenges are against incumbents with more liberal records than Lipinski on core issues such as abortion, which may make them less vulnerable.

It takes only one upset to rattle a party, however, said Robert Boatright, a political science professor at Clark University in Massachusetts.

“From the perspective of a group that wants to make a point in the primaries, all you need to do is go after one incumbent who is not paying attention,” he said.

Lipinski, co-chair of the moderate “Blue Dog” coalition in Congress, has influential support from the state AFL-CIO labor union federation.

His backers see the primary fight as a waste of liberal resources.

“We have so many other districts that we could focus on and try to pick up those seats,” said Kristen Day, executive director of the anti-abortion group Democrats for Life of America.