The Elector who took the most prominent part in this offer to Ottakar had been the Archbishop of Köln; but Werner of Mainz now succeeded in inducing the Archbishops of Köln and Trier to join him in an alliance which was to secure the election of an Emperor who would be amenable to their advice. Werner had been specially alarmed at the growth of Ottakar’s power; for any development of Bohemian independence would weaken the power of the Empire over the diocese of Prague, and would thereby weaken also the ecclesiastical authority of Mainz. He was, therefore, specially anxious to secure a counterbalancing power to Ottakar’s, but a power which would at the same time be dependent on the Electors of the Empire. The Archbishops first considered, and then rejected, the proposal to raise to the Imperial throne the Count Palatine of the Rhine; for they soon saw that he might be useful as an ally, but extremely dangerous as a master. As the great hindrance to the unity of the Empire seemed, at that time, to come from the South, it was particularly necessary for the Archbishops to win to their side Duke Louis of Bavaria, who was the principal rival and enemy of Ottakar. Bavaria had recently been divided into two parts, between the two brothers Louis and Henry; and the warm friendship of Henry for Ottakar had strengthened the opposition of Louis. Louis, indeed, may have himself dreamt of the Imperial crown; but neither the Archbishops, nor the more northern Electors, were disposed to concede this dignity to him. They had, however, a bait which was sufficiently attractive to the Duke.
It appeared that in the year 1257, the Duke of Bavaria had taken part in one of those confused elections to the Empire which had given an opportunity for every kind of irregular interference. The Archbishops now proposed to recognise this precedent as conferring on the Duke of Bavaria the position of Elector of the Empire, and thus completing the mystic number of seven, without the help of the King of Bohemia. A candidate for the throne had, however, still to be found; and, as the idea of choosing one of the more powerful princes was now definitely abandoned, the Margrave of Brandenburg and the Duke of Saxony put forward a kinsman of their own, named Siegfried of Anhalt.