ON MARCH 20th, Democrats and Republicans in Illinois are holding primaries to select their candidates for governor, 18 congressional seats, attorney-general, secretary of state and other local offices. The gubernatorial race is getting the bulk of media attention: Bruce Rauner, a singularly vulnerable Republican governor, is fighting for his political life. But the race in the third congressional district in the south-west of Chicago is unusually interesting: Dan Lipinski , a seven-term congressman is running neck-and-neck with Marie Newman, a marketing executive who has never before sought office.

The unexpectedly tight race is symptomatic of the deep division within the Democratic Party between those who want the party to move to the right on immigration, abortion and other social issues and those who want it to adopt the policies championed by Bernie Sanders, the liberal senator from Vermont who ran for the presidency in 2016. (Mr Sanders won the third district by eight percentage points in the presidential primaries.) Mr Lipinski is a pro-life Democrat who voted against President Barack Obama’s Affordable Care Act (ACA) as well as the DREAM act, a law providing a path to permanent residency for those who came to America as children of undocumented immigrants. He also chose not to sign the Equality act, which expands protections against discrimination on the basis of sexual orientation and gender identity. Ms Newman is pro-choice, a champion of lesbian, gay and transgender rights and a supporter of universal health care.

For a political newcomer like Ms Newman, Mr Lipinski is a formidable candidate to take on. He is co-chairman of the Blue Dog coalition, a small group of centrist Democrats. His seat has been in the family for 36 unbroken years; Mr Lipinski inherited it from his father, William, who went on to open a one-man lobbying firm. Over the years the Lipinskis built deep ties with Chicago’s Democratic machine. The Chicago Tribune and the Sun Times, the city’s main newspapers, are backing him. So is the AFL-CIO and many other local unions.

Mr Lipinski has repeatedly warned his party about moving too far to the left. “This is part of the reason Donald Trump won,” he said in an interview with the New York Times this month. “Democrats have chased people out of the party.” Mr Lipinski explained that he voted against the ACA because he considered it fiscally unsound and because, as a practising Catholic, he opposed the way the law funds and supports reproductive services. He now supports Obamacare and has voted against Republican efforts to repeal and replace it. And he is a co-sponsor of the bipartisan BRIDGE act, which would provide temporary protection from deportation for children of illegal immigrants.

Ms Newman argues that Mr Lipiniski is out of touch with the third district, which used to be predominantly Polish and Irish (and very Catholic) but has become more diverse over the last 15 years. Two-thirds of voters in the district are pro-choice. “It is time to dump this Trump Democrat,” says one of her television ads. She has been endorsed by Mr Sanders; Kirsten Gillibrand, a senator from New York with presidential ambitions; as well as NARAL Pro-Choice America; the Human Rights Campaign; the Service Employee International Union; MoveOn.org, a progressive advocacy group and Planned Parenthood, an advocacy group for reproductive rights. Even Luis Gutierrez and Jan Schakowsky, fellow congressmen from Illinois, are backing Ms Newman. A group called the Illinois Coalition for Immigrant and Refugee Rights Action has paid for Spanish-language television ads attacking Mr Lipinski on his voting record on immigration. (The population of the third district is now about one-third Hispanic.)

Mr Lipinski is narrowly leading in the latest polls conducted for one of Ms Newman’s allies, but it is a close call. Whoever wins will be elected in November. Arthur Jones, a septuagenarian neo-Nazi and Holocaust-denier, will be the candidate for the Republicans, because they could not be bothered to recruit a sound candidate for this deep-blue district. Mr Jones has unsuccessfully run for office for almost half a century.