When it is said that the question is only one of political morality, this does not extenuate its importance. Questions of constitutional morality are of no less practical moment than those relating to the constitution itself. The very existence of some governments, and all that renders others endurable, rests on the practical observance of doctrines of constitutional morality; traditional notions in the minds of the several constituted authorities, which modify the use that might otherwise be made of their powers. In unbalanced governments--pure monarchy, pure aristocracy, pure democracy--such maxims are the only barrier which restrains the government from the utmost excesses in the direction of its characteristic tendency. In imperfectly balanced governments, where some attempt is made to set constitutional limits to the impulses of the strongest power, but where that power is strong enough to overstep them with at least temporary impunity, it is only by doctrines of constitutional morality, recognized and sustained by opinion, that any regard at all is preserved for the checks and limitations of the constitution. In well-balanced governments, in which the supreme power is divided, and each sharer is protected against the usurpations of the others in the only manner possible, namely, by being armed for defense with weapons as strong as the others can wield for attack, the government can only be carried on by forbearance on all sides to exercise those extreme powers, unless provoked by conduct equally extreme on the part of some other sharer of power; and in this case we may truly say that only by the regard paid to maxims of constitutional morality is the constitution kept in existence. The question of pledges is not one of those which vitally concern the existence of representative governments, but it is very material to their beneficial operation. The laws can not prescribe to the electors the principles by which they shall direct their choice, but it makes a great practical difference by what principles they think they ought to direct it; and the whole of that great question is involved in the inquiry whether they should make it a condition that the representative shall adhere to certain opinions laid down for him by his constituents.