CHICAGO (Reuters) - Democratic Representative Dan Lipinski held off a stiff challenge from businesswoman Marie Newman to win a nationally watched congressional primary in Illinois that pitted a long-serving centrist incumbent against the party’s liberal wing.

Newman conceded on Wednesday morning, more than 12 hours after polls closed. With 97 percent of precincts reporting, Lipinski held on to a 51 percent to 49 percent lead.

“After reviewing the results, we know that we lost by a thin margin,” Newman said in a prepared statement.

Lipinski, one of a dwindling number of centrist House Democrats, had been re-elected easily since he inherited the seat from his father in 2004, despite breaking with his party frequently on social issues. He opposes abortion and gay marriage and he voted against the Democrats’ signature Affordable Care Act health law in 2010.

Newman said those positions were out of step with the Democratic party. She said her campaign had succeeded in pushing Lipinski to the left on immigration and health care, and vowed to keep up the pressure.

“I plan on continuing to hold him accountable so that every person in our district has access, opportunity, and equal rights,” she said.

The race drew national attention as an early test of whether the anti-Trump sentiment galvanizing the party’s base could also sweep some centrist lawmakers out of office.

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More than a dozen congressional Democrats across the country face credible challengers, mostly from the left, in nominating contests over the coming months that will determine the party’s candidates for November’s midterm elections.

Antipathy for Republican President Donald Trump is energizing Democratic races, raising the odds that they will pick up the 23 seats they need to win control of the House of Representatives and the two seats they need to win control of the Senate.

Lipinski argued that Democrats need to avoid ideological litmus tests if they want to win back the white working-class voters who have abandoned them in recent elections.

“Donald Trump was elected president because there were Democrats who felt like the Democratic Party was not standing up enough for working people,” he told Reuters on Tuesday.

Trump told Republican leaders at a dinner in Washington on Tuesday night that he will be traveling the country to campaign for his party’s candidates.

“They have gone so far left, we have to go a little further right,” Trump said of the Democrats.

Lipinski is heavily favored to win re-election in the fall. He will face Republican Art Jones, a Holocaust denier who has been disowned by his own party.