Parliament cannot simply vote a chancellor out
The Bundestag can remove a sitting chancellor through a constructive vote of no confidence. The mechanism requires parliament to elect a successor with an absolute majority at the same time. If that majority exists, the Federal President must dismiss the incumbent and appoint the newly elected chancellor.
The design deliberately raises the cost of bringing down a government. Opposition to the incumbent is insufficient by itself; a viable alternative majority must exist.
Why the mechanism changes coalition power
Because removal requires agreement on a successor, coalition disputes do not automatically translate into a successful no-confidence vote. Parties considering defection must ask not only whether they want the chancellor gone, but whether they are prepared to support the same replacement.
That gives parliamentary arithmetic a stabilising role. A politically weakened chancellor can remain in office if opponents cannot assemble an absolute majority around one alternative.
The chancellor is powerful but not solitary
The chancellor sets general policy guidelines, while ministers retain autonomy within their departments and the cabinet decides collectively on major interministerial disputes. Coalition agreements add a political constraint that sits alongside formal constitutional authority.