Germany’s Social Democrats have shot up in the polls since they asked Martin Schulz, the former European Parliament chief, to lead them into September’s election. But they may yet lose some of their newfound popularity if voters start thinking through the consequences.

The Social Democrats are neck and neck with Angela Merkel’s Christian Democrats in the polls. Whereas the right enjoyed a comfortable 10- to 15-point lead through all of last year, it would now struggle to place first.

Schulz has drawn support from all sides: moderate Christian Democrats, Greens and even anti-establishment voters who were planning to support the Alternative für Deutschland before he joined the contest.

That first group is most likely to switch back once they realize the Social Democratic Party could govern without the right if it grows big enough.

Far-left pact

Christian Odendahl, a German economist, argues that Schulz can no longer rule out a pact with the Die Linke.

The Social Democrats already rule in coalition with the far left in some cities and states.

The party, which descended from the former East Germany’s ruling communists, has also lost its monopoly on protest votes to the Alternative, according to Odendahl, making it more suitable for government.

Schulz maintains he has no interest in dealing with a party that wants to overthrow capitalism and withdraw Germany from NATO. But 68 percent of voters believe he would make a pact if the Social Democrats and Greens fell short of a majority on their own.

Only 30 percent approve of it, though. And that’s where Merkel comes in.

Mainstream options

Odendahl argues that her ruling out a coalition with the Alternative is both obvious and credible, meaning a vote for Merkel is a vote for another mainstream government. She could form another grand coalition with the Social Democrats or, if the numbers allow it, a center-left alliance with the Greens or a center-right pact with the liberal Free Democrats.

Scaremongering worked last time. In the 2013 election, Merkel argued that the only alternative to a right-wing government led by her Christian Democrats was a left-wing coalition with Die Linke.

That turned out to be false. When Merkel’s preferred coalition partner, the Free Democrats, lost their representation in parliament, she had no choice but to form a government with the Social Democrats. It didn’t seem to pain her. Her first government, from 2005 to 2009, was a grand coalition as well.

Little change

So long as the Christian Democrats remain in power, Odendahl sees little change in German policy.

The country would still resist the mutualization of debt in the form of eurobonds.

It would still oppose a European deposit insurance scheme.

It would not be any friendlier to Britain, which has yet to accept that the remaining 27 member states are not willing to compromise the EU’s core principle — the inseparability of the free movement of capital, goods, services and people — for the sake of a smooth Brexit.