BERLIN — The dispute over migration policy inside Chancellor Angela Merkel's conservative bloc has raised questions over the future of Germany's governing coalition, which took office only in March.

Merkel's Christian Democratic Union and Interior Minister Horst Seehofer's Christian Social Union have had a close partnership for seven decades. The CSU exists only in Bavaria, the CDU in Germany's 15 other states. The two conservative parties stay out of each other's territory, but campaign together in national elections and have a joint group in the federal parliament.

If the CSU were to depart the coalition, the government — a so-called "grand coalition" of Germany's biggest parties that also includes the center-left Social Democrats — would be two seats short of a majority in Germany's parliament.

The lower house, or Bundestag, elected in September has 709 seats. That means 355 are required for a majority, which is needed in a confidence vote or to elect a new chancellor, and Merkel's coalition has 399.

The CDU has 200 seats and the CSU 46. The Social Democrats have 153.

There are four opposition parties: the anti-migration and anti-establishment Alternative for Germany, which has 92 seats; the pro-business Free Democrats with 80; the hard-left Left Party with 69 and the Greens with 67. Two lawmakers who left Alternative for Germany last year sit as independents.