In parliamentary systems the head of state may be merely the nominal chief executive officer, heading the executive branch of the state, and possessing limited executive power. In reality, however, following a process of constitutional evolution, powers are usually only exercised by direction of a cabinet, presided over by a head of government who is answerable to the legislature. This accountability and legitimacy requires that someone be chosen who has a majority support in the legislature (or, at least, not a majority opposition – a subtle but important difference). It also gives the legislature the right to vote down the head of government and their cabinet, forcing it either to resign or seek a parliamentary dissolution. The executive branch is thus said to be responsible (or answerable) to the legislature, with the head of government and cabinet in turn accepting constitutional responsibility for offering constitutional advice to the head of state.