BERLIN — When Martin Schulz was named the Social Democratic candidate for chancellor, the party began a stellar ascent in the polls — a phenomenon dubbed the “Schulz effect” in the German capital.

This weekend, the Schulz effect will be put to the test.

Saarland — in Germany's southwestern corner and one of the least populous states — will elect a new regional parliament on Sunday. At any other time, the vote would have likely gotten little coverage outside the state capital Saarbrücken. But this year, ahead of Germany’s national election, it has generated intense interest in Berlin and beyond.

Observers see the vote as an early indication of how well the Schulz-revived Social Democrats (SPD) could do against Chancellor Angela Merkel's Christian Democratic Union (CDU).

Who will take home the trifecta?

It’s the first of three regional elections this spring and many believe that the road to the chancellery goes through the states.

Schulz, a former president of the European Parliament, suggested as much in his first speech after being made the party's candidate, telling his audience that his plan was to win elections “first in Saarland, then in Schleswig-Holstein, then in North Rhine-Westphalia, and eventually in the September national election.”

The Schulz effect may still upend the election.

Since then, the SPD has gained more than 10 percentage points in national polls, partly at the expense of Merkel's CDU.

The two parties are now virtually tied, with the SPD at 33 percent and the CDU at 32 percent, according to a recent Insa poll.

Against this backdrop, many conservatives fear that a loss this weekend could have a devastating knock-on effect in the elections to follow.

“It would be a disastrous signal for the CDU to lose another one of the only four state premiers the party has left,” said Hendrik Träger, who teaches political science at the University of Leipzig.

Currently, CDU appoints state premiers in four states plus Bavaria, which is governed by its sister party, the Christian Social Union. The SPD has nine state premiers among its ranks.

First we take Saarland, then we take Berlin

Rural Saarland, a patchwork of thickly forested hills, industrial areas and mining towns, appears to be a well-suited laboratory to test the Schulz effect: Its current government in Saarbrücken mirrors the situation at the national level.

Conservative state premier Annegret Kramp-Karrenbauer, 54, has governed since 2012 in a grand coalition with the Social Democrats as her junior partner — the same make-up as Merkel’s grand coalition in Berlin.

Voters in the state appear satisfied with Kramp-Karrenbauer’s government, with almost three-quarters saying they are happy with her governance, according to a recent poll.

But the Schulz effect may still upend the election.

The Social Democrats have risen from 25 percent to 33 percent, according to recent regional polls — putting them only 2 percentage points behind the CDU which is on 35 percent. A few months ago, the conservatives were at 40 percent.

The state premier has been trying to put distance between Saarland and what is happening on a national level.

Critics accuse Merkel of not doing enough to support the CDU's regional candidate

“The federal elections are being decided in September," she said at a campaign event earlier this month. "Now, in March, it's about our future. And we won’t have anyone else decide over it, no matter what their names are.”

Meanwhile, her challenger from the SPD, Saarland's current economy minister, Anke Rehlinger, is surfing the Schulz wave.

Until recently, few people in Berlin knew the 40-year-old, who has described herself as a “country bumpkin” and claims to have no political ambitions beyond the state borders. But when the SPD elected Schulz as party chief with an unprecedented 100 percent of the vote, it was Rehlinger, a lawyer and former professional athlete, who announced the spectacular result. The following day, newspapers across Germany carried photographs showing her side-by-side with Schulz and his predecessor Sigmar Gabriel.

Meanwhile, critics accuse Merkel of not doing enough to support the CDU's regional candidate, Kramp-Karrenbauer.

While the chancellor did travel twice to Saarland for campaign events, some within the party ranks criticize Merkel for being too slow to switch into campaign mode.

“Her strategy seems to be sacrificing three state elections ... during which a quarter of Germany goes to the ballots,” said a high-ranking CDU official, speaking on condition of anonymity.