Bavarian leader Markus Söder and Merkel loyalist Armin Laschet have both thrown their hats in the ring to run as the conservative bloc's candidate for German chancellor.
Sunday's elections in Spain's Catalonia region gave separatists a boost in the regional parliament.
Protesters say the president's term ended last Sunday; however, the incumbent insists he has another year left.
Exit polls suggest a commanding victory for the governing Nour Otan party, as more than 30 demonstrators were detained in Almaty and the capital, Nur-Sultan.
The opposition parties had wanted the vote to be delayed, alleging poor preparations and an electoral body influenced by the president.