The Christian Democrats (CDU) and its CSU Bavarian sister party were steady at 39 percentage points in the Emnid poll published in Bild am Sonntag newspaper, while the SPD fell one percentage point to 24.
The SPD had surged from 16 points behind the CDU/CSU in mid-January to a 33-32 lead in mid February after nominating Martin Schulz as chancellor candidate. The SPD held even with the CDU/CSU at 33-33 until early April before falling behind.
Merkel's conservatives won three regional elections in the last three months while the initial euphoria surrounding Schulz, a former European Parliament president, wore off.
Despite the widening lead, Merkel's CDU/CSU is far short of a majority and might have a difficult time finding a junior coalition partner. Their preferred partner, the Free Democrats (FDP) were steady at 7 percentage points in the Emnid poll.
The far right Alternative for Germany (AfD), ostracized by the other parties and without any coalition partner options, was steady at 8 percentage points
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)