A poll by opinion research institute Insa and Bild on Monday placed the Social Democrats (SPD) one percentage point ahead of Merkel's conservative Union parties, the CDU and CSU.
The SPD jumped up four percentage points over the last poll one week ago to reach 31 percent support over the Union's 30 percent - a drop of about three percentage points compared to last week.
Another poll by Emnid and Bild on Sunday saw the SPD make a “historic leap” - as Focus called it - of six percentage points compared to the previous week, which Bild said was the “biggest increase of all time”.
But the Emnid poll showed the SPD reaching 29 percent support, thus not beating out the Union parties at 33 percent support.
The SPD's success in the surveys comes on the heels of former EU Parliament President Martin Schulz officially becoming the party's chancellor candidate to face off against Merkel in the September election.
The Emnid poll also asked respondents to choose Schulz or Merkel, if hypothetically they were able to directly vote for a chancellor - German chancellors are not directly elected by the public, but by the parliament. Merkel received 41 percent of the theoretical vote, but Schulz came in close at 38 percent.
“Martin Schulz has succeeded above all in winning back former SPD voters and addressing them in an emotional away,” Emnid researcher Torsten Schneider-Haase told Bild.
“Such a powerful shift in party preference within a week is unparalleled.”
Merkel's other main concern as she runs for another term has been the upstart, populist Alternative for Germany (AfD), founded in 2013. The party failed to make it above the five percentage point threshold to earn seats in the German parliament (Bundestag) in its first year of operation, but polling over the past year shows it will likely gain seats this year.
The Insa poll showed the AfD at 12 percent, while the Emnid poll showed it at 16 percent support.