BERLIN — For the first time in the history of German politics, two women face off in a state election Sunday that will serve as a referendum on Angela Merkel's policies — and a measure of the relative strength of the two partners in her 'grand coalition' government.

Malu Dreyer, a Social Democrat (SPD), and Julia Klöckner of Merkel’s conservative Christian Democrats (CDU), are neck-and-neck in the southwestern wine-producing state of Rhineland-Palatinate, one of three German states holding elections Sunday.

With both candidates at 35 percent, neither Dreyer, the incumbent state premier, nor her challenger Klöckner, are pulling any punches, even though the CDU and SPD are coalition partners in the federal government.

“Rhineland-Palatinate can do better. We deserve a change,” Klöckner said in a televised debate last week.

Dreyer, in an interview with NTV, touted what she described as her proven leadership qualities: “I am a clear-thinking, analytical and reliable woman. I can make tough decisions, but I also have an open heart. I stand for cohesion in the state, and Mrs. Klöckner divides the state.”

Since Merkel became chancellor in 2005, women have taken up top government ministries like defense and labor, a major advance on their longtime relegation to traditional 'women's' portfolios like the family ministry that Merkel herself held under the chancellorship of Helmut Kohl.

Women have also risen to prominent roles in regional politics, with a woman serving as premier in Germany's most populous state, North Rhine-Westphalia, and as mayor of Germany's fourth largest city, Cologne.

National interest in the Rhineland-Palatinate election is heightened by the media's fascination with a woman they have anointed as Merkel's "crown princess:" 43-year-old Klöckner, who is touted as a potential successor to 61-year-old Merkel if she can earn her political spurs by winning back the state for the CDU, after 25 years in the hands of the SPD.

Klöckner looked set for success until the refugee crisis — and Merkel's handling of it — became one of the hottest issues in the campaign.

Wine queen

The CDU desperately needs Klöckner to win Rhineland-Palatinate in order to put an end to a string of state election losses on Merkel's watch: Of the 16 German federal states, the CDU and their Bavarian sister party, the CSU, form part of the regional government in only seven.

As recently as November, Klöckner had a 10-point leader over Dreyer with 41 percent support in opinion polls. But as hundreds of thousands of refugees kept pouring into the country, encouraged by Merkel's open-doors policy and her "We can manage" slogan, Klöckner and the CDU took a kicking, losing support to the anti-immigrant Alternative für Deutschland (AfD).

In panic, Klöckner drew up her own strategy for the refugee crisis and took issue with Merkel's refusal to put a limit on the number of refugees Germany will take. This was a fatal mistake, according to CDU officials in Berlin, who believe the candidate's so-called "alternative plan" is being interpreted by voters as veiled criticism of Merkel.

The German media went even further, saying Merkel’s crown princess had deserted her queen — prompting Klöckner in turn to waste precious time on the campaign trail pledging allegiance to the chancellor rather than attacking her rival, Dreyer.

Dreyer saw her opportunity, and made the most of it: She simply joined her challenger's conservative critics, accusing Klöckner of stabbing Merkel in the back. In party political terms, it was a no-brainer, since her SPD is behind the chancellor's welcoming stance on the refugees, as much as it might disagree on how best to integrate the new arrivals.

The CDU candidate blends a progressive view on social issues with a sometimes dismissive attitude to immigrants. A student of Catholic theology, she worked as a food and wine journalist for a decade before being elected to the national parliament in Berlin in 2006.

In a party which is still dominated by grey-haired old men, despite Merkel's influence, the former “wine queen” — a title awarded annually at the beauty pageant held by wine producers in Rhineland-Palatinate — has a broad smile and confidence that makes her supremely effective at working crowds in the beer tents and wine gatherings.

A progressive on social issues, meaning that despite her Catholicism she supports allowing same-sex marriages in church, the CDU candidate speaks out for gender equality. On the campaign trail, she said the key to Muslims' integration into German society was their acceptance of women as men's equals. Klöckner said she would not meet an imam who refused to shake her hand and dismissed refugees who turned down food served by women, saying: "They have already eaten then, I guess."

Ministry for wine

Dreyer is a challenging opponent.

A 55-year-old, soft-spoken lawyer and former district attorney, the SPD politician was diagnosed with multiple sclerosis in 1994 and sometimes uses a wheelchair.

This may be why Klöckner visibly holds back when they debate. All the same, Dreyer has a 50 percent personal approval rating in the state, putting her far ahead of Klöckner, who gets 30 percent approval. Dreyer is anything but frail in their debates.

“I am governing this state with great passion,” Dreyer said in one televised debate. “Do you actually live here?” she asked Klöckner, who spent 11 years working in Berlin as a member of the federal parliament and a deputy farm minister before returning to her native state in 2011.

With its picturesque hills and sprawling vineyards, Rhineland-Paletinate is far from the hustle and bustle of Berlin. The 7th largest federal state, it is the only one with a ministry for wine growing, though it's not the only industry in the export-strong state: BASF has its headquarters there, in the city of Ludwigshafen.

Klöckner's long absence exposes her to criticism that she is only running for state premier to raise her profile in the big league of politics, with aspirations to become a federal minister in Berlin — or even chancellor.

But the SPD has much to lose in Rhineland-Palatinate: it faces catastrophic losses in the two other German states up for election on Sunday, and needs Malu Dreyer to win what party chief Sigmar Gabriel, who is deputy chancellor in Merkel's 'grand coalition' government, has described exaggeratedly as the "mother of all battles."