The Texas treaty of annexation was still pending in the Senate with a decided majority committed against its confirmation, both upon public and partisan grounds. The Whig senators and the friends of Van Buren had coalesced for its defeat after their respective chiefs had pronounced against it. Mr. Crittenden of Kentucky and Colonel Benton were the leaders under whose joint efforts the work of Calhoun was to be set at naught. But, in fact, the work of Calhoun had already been effectually done and he could afford to disregard the fate of the treaty. He had consolidated the Democratic delegates from the slave-holding States against Mr. Van Buren, and the decree had gone forth for his political destruction. Mr. Van Buren, with the aid of the more populous North, had indeed secured a majority of the convention, but an instrumentality was at hand to overcome this apparent advantage. In the two preceding national conventions of the Democratic party, the rule requiring a two-thirds vote of all the delegates to make a nomination had been adopted at the instance of Mr. Van Buren's friends in order to insure his victory. It was now to be used for his defeat. Forseeing the result, the same zealous and devoted friends of Mr. Van Buren resisted its adoption. Romulus M. Sanders of North Carolina introduced the rule, and was sustained with great vigor by Robert J. Walker of Mississippi, and George W. Hopkins of Virginia. The leading opponents of the rule were Marcus Morton of Massachusetts, Nathan Clifford of Maine, and Daniel S. Dickinson of New York. The discussion was conducted by Southern men on one side and by Northern men on the other,--the first division of the kind in the Democratic party. Slavery was the ominous cause! The South triumphed and the rule was fastened upon the convention. Immediately after this action Mr. Van Buren received a majority of the votes on the first ballot, and it was not unnaturally charged that many of those supporting him must have been insincere, inasmuch as they had the full right, until self-restrained by the two-thirds rule, to declare him the nominee. But this conclusion does not necessarily follow. Mr. Van Buren had been nominated in the National Democratic Conventions of 1835 and 1839 with the two-thirds rule in operation; and now to force his nomination for a third time by a mere slender majority was, in the judgment of wise and considerate party leaders among his own friends, a dangerous experiment. They instinctively feared to disregard a powerful and aggressive minority stubbornly demanding that Mr. Van Buren should be subjected to the same test which his friends had enforced in previous conventions. Their argument was not satisfactorily answered, the rule was adopted, and Mr. Van Buren's fate was sealed. CALHOUN DEFEATS VAN BUREN.