CSU General Secretary Markus Blume sees the decision for Armin Laschet as candidate for chancellor to be the cause of the Union's poor poll results.
"Of course we would be better off with Markus Söder," said Blume on Thursday of the magazine "Spiegel".
"The consistently high approval ratings for Markus Söder show what potential we actually have as a Union - we now have to raise that together in the remaining two weeks."
In April, Laschet had prevailed against Söder within the Union for the candidacy for chancellor.
In the meantime, the Union is behind the SPD in the polls, and the CSU is threatened with the worst election result in decades in Bavaria.
Blume said there was “a very strong influence of the federal trend in federal elections”.
"We cannot free ourselves from that either."
The accusation that Söder made life difficult for Laschet with his taunts was called "a sham argumentation" by Blume.
According to the report, the CSU had already prepared appropriate posters for the case of Söder's candidacy for chancellor.
“Ready for Germany” would have been the slogan, said Blume.
According to “BayernTrend”, the CSU currently receives 28 percent of the vote, eight percentage points less than in an Infratest Dimap survey at the beginning of July.
Four years ago, the Christian Socialists received 38.8 percent of the vote in Bavaria.
The Allensbach survey on behalf of the FAZ last saw the Union at 25 percent, the SPD at 27 percent.
The Social Democrats gained three percentage points compared to the previous survey.
According to Allensbach, the Greens fell from 17 to 15.5 percent.
For the first time in a long time, the FDP is below ten percent.
Allensbach found 9.5 percent for the Liberals.
The AfD has eleven percent, the Left Party six.
A total of 1258 people were interviewed for the representative survey between September 1st and 7th.