BERLIN — Germany’s liberal Free Democratic Party is on the verge of resurrection and eager to challenge the status quo, whether the issue is Greece, Trump or even that holiest of all German subjects — the economy.

“Overall, there’s a deceptive feeling of economic invincibility in Germany,” FDP leader Christian Lindner told POLITICO, saying the economy could become “the biggest challenge for the coming years. We find ourselves on a historically high plateau in Germany, but the end is on the horizon.”

Following a string of strong showings in regional elections, the FDP has polled well at the national level, reaching a high of 10.5 percent in a survey published Tuesday by the respected Allensbach Institute. If the polls are borne out at the ballot box in September, the FDP would be in good position to join a government led by Angela Merkel’s conservatives.

That may not seem surprising, given the liberals’ long history of alliances with Merkel’s center-right bloc. Except that the Free Democrats haven’t seen the inside of the German parliament since 2013, when they suffered a humiliating general election thrashing that left the party without any seats in the Bundestag for the first time since 1949.

Even if the FDP ends up joining the government as many expect, it’s unlikely to play the pliable sidekick of old. Four years in the political wilderness have left the the party leaner, meaner and itching to fight for its core liberal values.

The credit for the FDP’s budding comeback rests largely with its youthful leader. A former adman turned full-time politician, Lindner, 38, has returned the FDP to its liberal roots and sharpened its tone.

When it comes to his economic vision for the European Union, Lindner is the “anti-Macron.”

In a wide-ranging interview in his Berlin office, he made clear he wasn't afraid to take on his party's longtime allies in Merkel's Christian Democrats.

Perhaps most controversially, he said Greece should be granted debt relief and forced out of the euro on a temporary basis until its economy recovers, despite the hard-fought deal Athens reached last week with its creditors.

“Debt relief has to be combined with at least a temporary departure from the eurozone,” Lindner said. “A separate currency for Greece carries risks, but also marks a strategic change with new opportunities for Athens.”

Allowing Greece to remain while writing off some of its debts would create “moral hazard,” he warned, and be unfair to countries such as Portugal that have coped with harsh strictures of a bailout program in recent years.

The idea for Greece to exit was originally floated by German Finance Minister Wolfgang Schäuble at the height of the Greek crisis in 2015 but later dropped after Athens agreed to Europe’s tough bailout conditions.

Lindner said Greece should remain a member of the EU but vowed to withhold his signature from any deal on debt forgiveness that would allow Greece to remain in the common currency.

That’s significant because the deal agreed last week between Greece, its creditors and the IMF to end a more than year-long standoff would need the endorsement of Germany's next government in order to go forward. Lindner said the pact, endorsed by Berlin, constituted a violation of the bailout terms approved by the German parliament in 2015.

Lindner’s position is one shared by many in Merkel’s Christian Democratic Union and its Bavarian sister party, the Christian Social Union, suggesting that if the parties do form a government, the question of how to deal with Greece could be on the front burner again.

Macron’s 'Soviet' system

When it comes to his economic vision for the European Union, Lindner is the “anti-Macron.”

Although he sports striking similarities with the French president — both are charismatic leaders of centrist parties in their late 30s — the German liberal left no doubt that he believes Macron’s ideas for EU reforms will do economic and political harm to the bloc.

“Macron suggests to move towards standardization and, eventually, pooling debt,” he said, warning that this process will lead to “a Soviet Union-style system, in which at some point, the systematic losers will turn against the European Union and the euro.”

It’s something you do not hear often in the German capital these days.

Since Emmanuel Macron won the French presidency campaigning on a staunchly pro-EU platform last month, German Chancellor Angela Merkel and her Social Demcoratic challenger Martin Schulz have increased the emphasis on Europe in their campaigns.

Part of both of their strategies: Claim Macron as one of their own.

Schulz, a former president of the European Parliament, said earlier this month that the new French leader "needs a dynamic politician with experience in European politics as his partner.”

This week, Merkel used an appearance in front of Germany’s business lobby to endorse some of Macron’s suggestions for the eurozone.

Don’t expect Lindner to join their choir.

He stressed that he was happy about the pro-EU candidate winning the presidency instead of far-right nationalist Marine Le Pen, but slammed Macron’s key suggestions for European reforms.

The eurozone needs neither a budget or a parliament of its own, he said.

Handing the reins to the youthful Lindner, the party’s former general secretary, was seen by many as an act of desperation in 2013.

Instead, Lindner believes it’s time to toughen up on rules inside the EU, which could include linking EU subsidies to adhering to budget rules.

Instead of pursuing a new master plan to force EU countries to integrate, Lindner said he supported a "Europe of diversity." If Germany and France, for example, wanted to harmonize corporate tax rates, they should do so, but others shouldn't be compelled to follow. He also rejected the idea of requiring non-euro countries such as Poland to join the currency area.

“When it comes to the question whether all EU member states should join the euro, I don’t share [European Commission President Jean-Claude] Juncker’s euphoria without reservation,” he said. “The eurozone has a number of systematic and economic problems that need to be solved before we can expand the circle.”

Bastion of economic reason

When Lindner took over in 2013, his party was in ruins. Just four years earlier, a triumphant FDP had joined Merkel’s government after winning 15 percent of the vote, a record for the party. Once in power, however, its leadership faltered and failed to make good on a campaign promise to push through tax cuts.

The FDP’s defeat was so total that some observers doubted it would ever recover. Handing the reins to the youthful Lindner, the party’s former general secretary, was seen by many as an act of desperation.

As it sought to broaden its appeal over the years, the FDP had strayed from its traditional focus on self-determination anchored in individual freedom. Lindner has taken it back there, while also embracing a conservative approach to law and order.

The clearest indication that the strategy is resonating came in May in North Rhine-Westphalia, Germany’s most populous state.

In a regional election widely considered a key indicator of the national mood ahead of September's parliamentary poll, the FDP — whose campaign was spearheaded by Lindner — won more than 12 percent of the vote, four percentage points higher than their 2012 result.

But the party knows it will have to work hard to stand out from the crowd in the national campaign, as it goes up against high-profile figures such as Merkel, Europe's pre-eminent leader, and Schulz.

A big part of Lindner’s strategy is to push the image of his FDP, long a favorite of the business community, as a bastion of economic rationalism.

For Lindner, that means making sure the EU and Britain maintain a close relationship after Brexit. Germany has “a great interest … in a strong and economically prosperous Great Britain,” he said. It also means Germany should not turn away from the United States as one of its most important global partners — no matter which president resides in the White House.

“We continue to depend on the U.S. as our partner when it comes to economic and security policy,” Lindner said.

Read the full interview in German here.