In parliamentary systems, governments are generally required to have the confidence of the lower house of parliament (though a small minority of parliaments, by giving a right to block supply to upper houses, in effect make the cabinet responsible to both houses, though in reality upper houses, even when they have the power, rarely exercise it). Where they lose a vote of confidence, have a motion of no confidence passed against them, or where they lose supply, most constitutional systems require either:

Most parliamentary governments need to have the support of what governmental body?