An exit poll from the Saxony-Anhalt election for public broadcaster MDR had the Christian Democrats (CDU) on 36%, up more than 6 points on five years ago, and far ahead of the far-right Alternative for Germany (AfD), who were on 22.5%, slightly down on the previous election.
Laschet, a centrist, was seen as having made an uncertain start to his election campaign and had faced calls to chart a more right-wing course to win back voters disenchanted by 16 years of compromises under Merkel.
"We have won the election," Saxony-Anhalt state premier Reiner Haseloff said after the exit polls came out. "A great majority of our citizens have said we don't want to be associated with the AfD. And for that I'm grateful."
He and other conservatives hailed the result as a tailwind for them ahead of the federal election.