Berlin (CNN)The race to succeed Angela Merkel as German chancellor remains wide open ahead of a national election on Sunday, according to the latest polls.
Poll predictions on Saturday point to the center-left Social Democrats (SPD) holding a small but narrowing lead over Merkel's party, the center-right Christian Democratic Union (CDU).
Merkel has been a symbol of stability in Europe since she took on the role of chancellor in 2005. But after almost 16 years in the top job, she will step down once it becomes clear who her successor will be.
The closeness of the race coupled with Germany's complicated voting system means it could take some time before a winning coalition is formed and the ultimate victor is known.
Environmental concerns and economic worries have emerged as key issues in campaigning, with the former fueled by the deadly floods that devastated parts of Germany this summer.
The SPD and CDU, the two largest parties in German politics, have been sharing power under Merkel's fourth term as chancellor.
CDU leader Armin Laschet, the party's candidate to be the next chancellor and premier of North Rhine-Westphalia, held a final campaign rally with Merkel in Aachen on Saturday.
A boy presented Merkel, 67, with a gingerbread heart iced with the words "Thanks CDU," and another supporter gave her a cake decorated with a picture of her trademark rhombus hand gesture.
Addressing the crowds, Merkel said Sunday's election was all about Germany remaining "stable" and ensuring "that the youth have a future and we can live in prosperity." She added that Laschet had shown throughout his political life that he could pursue it "with passion and heart."
Rival candidate Olaf Scholz, from the Social Democrats, held his last rally Saturday in his constituency in Potsdam. Scholz has been serving as the vice-chancellor and German finance minister since 2018.
Scholz told supporters that if elected, he wanted to agree an increase in the minimum wage to 12 euro ($14) an hour within the first year of government. "I want to achieve that those who work so hard, and earn little, have it a little better," he said.
Scholz also referenced the concerns many voters have over climate change. Many young people demonstrated Friday, he said, "and they put their fingers in a wound that is real -- because global climate change has to be stopped and we have to make our contribution here in Germany to make that happen."
FDP leader Christian Lindner was to end his election campaign with rallies in Cologne and Düsseldorf.
According to the latest polls, the Social Democrats are polling at 25.2% and could gain 4.7 percentage points compared to the 2017 national elections. This lead could mean a reversal of a 20-year-long downward trend for the Social Democrats. Over the past two decades, the party has lost around half of its voters.
The Christian Democrats are trailing several percentage points behind the SPD at around 22.4%, polls indicate. This could mean a loss of 10.5 percentage points compared to the 2017 national elections, and of 19.1 percentage points compared to the 2013 elections.
The Greens are currently polling at 15.9%, in third place. However, the ecological party could record the strongest growth of all parties in the next federal election, with a potential gain of 7.5 percentage points compared to the last national elections in 2017. The Greens' leader, Annalena Baerbock, has emerged as a contender for chancellor and potential kingmaker in the coalition negotiations expected to follow Sunday's vote.
Germany's business-friendly Free Democratic Party (FDP) is polling at 11.1% and is slated to make only marginal gains compared to the last national elections, according to poll predictions.
The far-right Alternative for Germany party (AfD) is polling at 10.6% -- a decrease of 2 percentage points compared to the 2017 national elections.
The AfD -- which saw a marked success in the 2017 elections following the influx of refugees into Germany in 2015 -- has struggled to keep its momentum going since and has faced harsh criticism over ties to the extreme far-right.