Between 1890 and 1914 the Center party was, in Friedrich Naumann's words, “the measure of all things” in German politics. Throughout this period it possessed a quarter of the seats in the Reichstag, and held the balance of power between left and right. Its importance from the standpoint of Bismarck's successors as chancellor stemmed from the electoral and parliamentary decline of the National Liberals and Conservatives, the parties which had formed theKartell through which Bismarck governed the Reichstag. After 1890 these no longer commanded a majority, and other parties had to be won over by the government. With the Social Democrats permanently hostile, this narrowed the government's choice down to the Progressives and Center, either of which would give the Kartell parties a majority, and both of which were to be used to this effect. However, the Progressives were used only sparingly (above all during the Biilow Bloc of 1907–9) because of their increasing shift to the left. The historic reason for this was the party's antimilitarism; and this move to the left was reinforced by fears among Progressive leaders that their supporters might otherwise defect to the Social Democrats. The Center was therefore the only alternative. For most of the Wilhelmine period successive chancellors depended for their parliamentary majorities on the Center, which in turn showed itself willing to become a “party of government.”