By the following spring the policy of Mr. Polk had culminated, intrigue had done its perfect work, hostilities had been brought on with Mexico, and in May Congress was invited to declare a war which the administration had taken care should already exist. Mr. Webster was absent at this time, and did not vote on the declaration of war; and when he returned he confined himself to discussing the war measures, and to urging the cessation of hostilities, and the renewal of efforts to obtain peace.
The next session—that of the winter of 1846-47—was occupied, of course, almost entirely with the affairs of the war. In these measures Mr. Webster took scarcely any part; but toward the close of the session, when the terms on which the war should be concluded were brought up, he again came forward. February 1, 1847, Mr. Wilmot of Pennsylvania introduced the famous proviso, which bears his name, as an amendment to the bill appropriating three millions of dollars for extraordinary expenses. By this proviso slavery was to be excluded from all territory thereafter acquired or annexed by the United States. A fortnight later Mr. Webster, who was opposed to the acquisition of more territory on any terms, introduced two resolutions in the Senate, declaring that the war ought not to be prosecuted for the acquisition of territory, and that Mexico should be informed that we did not aim at seizing her domain. A similar resolution was offered by Mr. Berrien of Georgia, and defeated by a party vote. On this occasion Mr. Webster spoke with great force and in a tone of solemn warning against the whole policy of territorial aggrandizement. He denounced all that had been done in this direction, and attacked with telling force the Northern democracy, which, while it opposed slavery and favored the Wilmot Proviso, was yet ready to admit new territory, even without the proviso. His attitude at this time, in opposition to any further acquisition of territory on any terms, was strong and determined, but his policy was a terrible confession of weakness. It amounted to saying that we must not acquire territory because we had not sufficient courage to keep slavery out of it. The Whigs were in a minority, however, and Mr. Webster could effect nothing. When the Wilmot Proviso came before the Senate Mr. Webster voted for it, but it was defeated, and the way was clear for Mr. Polk and the South to bring in as much territory as they could get, free of all conditions which could interfere with the extension of slavery. In September, 1847, after speaking and voting as has just been described in the previous session of Congress, Mr. Webster addressed the Whig convention at Springfield on the subject of the Wilmot Proviso. What he then said is of great importance in any comparison which may be made between his earlier views and those which he afterwards put forward, in March, 1850, on the same subject. The passage is as follows:—
"We hear much just now of a panacea for the dangers and evils of slavery and slave annexation, which they call the 'Wilmot Proviso.' That certainly is a just sentiment, but it is not a sentiment to found any new party upon. It is not a sentiment on which Massachusetts Whigs differ. There is not a man in this hall who holds to it more firmly than I do, nor one who adheres to it more than another.
"I feel some little interest in this matter, sir. Did I not commit myself in 1837 to the whole doctrine, fully, entirely? And I must be permitted to say that I cannot quite consent that more recent discoverers should claim the merit, and take out a patent.
"I deny the priority of their invention. Allow me to say, sir, it is not their thunder.
"There is no one who can complain of the North for resisting the increase of slave representation, because it gives power to the minority in a manner inconsistent with the principles of our government. What is past must stand; what is established must stand; and with the same firmness with which I shall resist every plan to augment the slave representation, or to bring the Constitution into hazard by attempting to extend our dominions, shall I contend to allow existing rights to remain.
"Sir, I can only say that, in my judgment, we are to use the first, the last, and every occasion which occurs, in maintaining our sentiments against the extension of the slave-power."
In the following winter Mr. Webster continued his policy of opposition to all acquisitions of territory. Although the cloud of domestic sorrow was already upon him, he spoke against the legislative powers involved in the "Ten Regiment" Bill, and on the 23d of March, after the ratification of the treaty of peace, which carried with it large cessions of territory, he delivered a long and elaborate speech on the "Objects of the Mexican War." The weight of his speech was directed against the acquisition of territory, on account of its effect on the Constitution, and the increased inequality of representation which it involved. He referred to the plan of cutting up Texas so as to obtain ten senators, as "borough mongering" on a grand scale, a course which he proposed to resist to the last; and he concluded by denouncing the whole project as one calculated to turn the Constitution into a curse rather than a blessing. "I resist it to-day and always," he said. "Whoever falters or whoever flies, I continue the contest."
In June General Taylor was nominated, and soon after Mr. Webster left Washington, although Congress was still in session. He returned in August, in time to take part in the settlement of the Oregon question. The South, with customary shrewdness, was endeavoring to use the territorial organization of Oregon as a lever to help them in their struggle to gain control of the new conquests. A bill came up from the House with no provision in regard to slavery, and Mr. Douglas carried an amendment to it, declaring the Missouri Compromise to be in full force in Oregon. The House disagreed, and, on the question of receding, Mr. Webster took occasion to speak on the subject of slavery in the territories. He was disgusted with the nomination of Taylor and with the cowardly silence of the Whigs on the question of the extension of slavery. In this frame of mind he made one of the strongest and best speeches he ever delivered on this topic. He denied that slavery was an "institution;" he denied that the local right to hold slaves implied the right of the owner to carry them with him and keep them in slavery on free soil; he stated in the strongest possible manner the right of Congress to control slavery or to prohibit it in the territories; and he concluded with a sweeping declaration of his opposition to any extension of slavery or any increase of slave representation. The Oregon bill finally passed under the pressure of the "Free-Soil" nominations, with a clause inserted in the House, embodying substantially the principles of the Wilmot Proviso.
When Congress adjourned, Mr. Webster returned to Marshfield, where he made the speech on the nomination of General Taylor. It was a crisis in his life. At that moment he could have parted with the Whigs and put himself at the head of the constitutional anti-slavery party. The Free-Soilers had taken the very ground against the extension of slavery which he had so long occupied. He could have gone consistently, he could have separated from the Whigs on a great question of principle, and such a course would have been no stronger evidence of personal disappointment than was afforded by the declaration that the nomination of Taylor was one not fit to be made. Mr. Webster said that he fully concurred in the main object of the Buffalo Convention, that he was as good a Free-Soiler as any of them, but that the Free-Soil party presented nothing new or valuable, and he did not believe in Mr. Van Buren. He then said it was not true that General Taylor was nominated by the South, as charged by the Free-Soilers; but he did not confess, what was equally true, that Taylor was nominated through fear of the South, as was shown by his election by Southern votes. Mr. Webster's conclusion was, that it was safer to trust a slave-holder, a man without known political opinions, and a party which had not the courage of its convictions, than to run the risk of the election of another Democrat. Mr. Webster's place at that moment was at the head of a new party based on the principles which he had himself formulated against the extension of slavery. Such a change might have destroyed his chances for the presidency, if he had any, but it would have given him one of the greatest places in American history and made him the leader in the new period. He lost his opportunity. He did not change his party, but he soon after accepted the other alternative and changed his opinions.