Seehofer is neither from Saxony-Anhalt, nor a member of the Christian Democrats. State prime minister of far-off Bavaria, he is the leader of that region's "sister party", the Christian Social Union (CSU).
But as several key states headed to regional elections today, Merkel has become a "toxic brand" for the Christian Democrats' core constituency.
Figures like Seehoffer are seen as far more likely to bring out the vote, even though they oppose their own government's policy on the biggest issue of the day.
Merkel does not face national elections until next year, but with CDU support falling in the polls, some are warning a poor showing in the state elections could make the party panic and look for a new leader.
"Angela Merkel may have won some new voters with her refugee policy, but she's losing traditional CDU voters," said Martin Beier, a 25-year-old party volunteer. The law student said his impression from canvassing was that many traditional CDU voters were "looking for an alternative".
Merkel's personal national approval ratings surged an unexpected eight points this month, to 54 per cent, but that may not mean much now if the party turns against her.