Open this photo in gallery Baden-Wuerttemberg Minister-President Winfried Kretschmann, seen addressing a news conference in Berlin on Sept. 11, 2018, has promoted not just traditional Green party policies, including generous social programs and a global climate-change compact, but also a lot of law and order to attract disillusioned conservative voters. HANNIBAL HANSCHKE/OP-SAUNDERS-GREENS-1102

If centre-left political parties are dreading a further loss of voters to the angry fringes – whether Democrats facing a tough struggle in next week’s U.S. midterm elections or Liberals fearing slashed margins in next year’s federal vote – they might want to pay a visit to this prosperous corner of Germany.

Here in Stuttgart, the heart of Germany’s automobile industry and the capital of the booming state of Baden-Wuerttemberg, they could take some lessons in hardball electoral strategy from a man who is frequently ranked as his country’s most popular politician. Winfried Kretschmann, who has served as Minister-President of this state since 2011, is also the parliamentary chairman of the Greens, which governs in a surprisingly congenial coalition with the conservative Christian Democrats – a party his Greens are close to equalling on the national level. He has huge influence over his party’s state and national branches.

The Kretschmann approach, as he recently described it to me and my colleagues, is to recognize that disillusioned conservative voters are reachable by left-leaning parties and can be deflected away from the temptations of the far right. But that means doing things that will seem distasteful or illogical to much of the party membership.

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The Greens, following his example, are soaring in popularity. In two recent important state elections and in this week’s national opinion polls, they have become the country’s second-ranked party, approaching the levels of Chancellor Angela Merkel’s dwindling Christian Democrats and far exceeding any other party. At this rate, they will very likely be partners in the next national government.

The Greens seem to have single-handedly put a stop to the most significant and frightening recent development in German politics, the hemorrhage of voters from mainstream conservative parties to the extreme-right Alternative for Germany (AfD), whose platform of opposition to racial and religious minorities has the distinct scent of Germany’s darkest moments.

The AfD has stalled this year (albeit at a still-alarming 15-per-cent support in polls) and that’s largely because disgruntled conservative voters are now switching not to the AfD, but to the Greens. In state elections, the Greens have attracted more new voters from the right than from the left, and the main voting destination for former Christian Democrats is now the Greens. Their rise, more than the AfD’s, provoked Ms. Merkel to announce this week that she’d be stepping down before the 2021 election to save her party.

How did the Greens get to this position?

“We realized that people are turning toward extremist parties not because they believe their ideas, but because they feel that the government doesn’t have things under control,” Mr. Kretschmann said. “So we listened to them.”

This is not the sandal-wearing image of the Greens, to the chagrin of some members and leaders. When Mr. Kretschmann spoke with my colleagues and me shortly before I visited his state, he came across as a flinty silver-haired burgher in wire-rim glasses and a tailored suit. Fitting this image, the policies he chose to boast about included generous social programs and a global climate-change compact – but also a lot of law and order.

His party’s signature policy in Baden-Wuerttemberg this year was to greatly, and expensively, increase the size of the police force. This, he happily acknowledged, makes no sense: Crime rates in his state, and across Germany, are at three-decade lows. But the Greens discovered that a lot of voters, in the wake of the 2015-16 migration crisis, were believing popular notions about immigrants and crime.

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He and the cabinet could have tried to convince everyone that this was nonsense: The crime rate fell sharply during and after the migration crisis. Instead, they decided to address the fears by spending money.

“My state is very well off; it has budget surpluses at all levels of government and full employment; we are paying off debts. But still, people are voting for the AfD. Their feeling that the government was not in control is registering at the ballot box.”

So he added more cops (why not, anyway?) and he pushed publicly for more border security and tougher, quicker deportation policy for the hundreds of thousands of migrants who don’t qualify as refugees. Tellingly, his party didn’t call for less immigration – his highly multicultural state has gaping needs for new population and he believes those voters weren’t concerned about immigration itself, just a sense of powerlessness.

“Now, there’s a feeling that the government is in control and we’re doing things,” he said. And that feeling has translated into votes. More traditional Greens have so far stayed on board, their fingers crossed that they will weaken far-right momentum without fatally compromising their own party’s principles.