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.