The cup of forbearance had been exhausted even before the recent information from the frontier of the Del Norte [the Rio Grande]. But now, after reiterated menaces, Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon the American soil…

As war exists, notwithstanding all our efforts to avoid it, exists by the act of Mexico herself, we are called upon by every consideration of duty and patriotism to vindicate with decision the honor, the rights, and the interests of our country.

Polk spoke of the dispatch of American troops to the Rio Grande as a necessary measure of defense. As John Schroeder says (Mr. Polk's War): "Indeed, the reverse was true; President Polk had incited war by sending American soldiers into what was disputed territory, historically controlled and inhabited by Mexicans."

Congress then rushed to approve the war message. Schroeder comments: "The disciplined Democratic majority in the House responded with alacrity and high-handed efficiency to Polk's May 11 war recommendations." The bundles of official documents accompanying the war message, supposed to be evidence for Polk's statement, were not examined, but were tabled immediately by the House. Debate on the bill providing volunteers and money for the war was limited to two hours, and most of this was used up reading selected portions of the tabled documents, so that barely a half-hour was left for discussion of the issues.

The Whig party was presumably against the war in Mexico, but it was not against expansion. The Whigs wanted California, but preferred to do it without war. As Sehroeder puts it, "theirs was a commercially oriented expansionism designed to secure frontage on the Pacific without recourse to war." Also, they were not so powerfully against the military action that they would stop it by denying men and money for the operation. They did not want to risk the accusation that they were putting American soldiers in peril by depriving them of the materials necessary to fight. The result was that Whigs joined Democrats in voting overwhelmingly for the war resolution, 174 to 14. The opposition was a small group of strongly antislavery Whigs, or "a little knot of ultraists," as one Massachusetts Congressman who voted for the war measure put it.

In the Senate, there was debate, but it was limited to one day, and "the tactics of stampede were there repeated," according to historian Frederick Merk. The war measure passed, 40 to 2, Whigs joining Democrats. Throughout the war, as Sehroeder says, "the politically sensitive Whig minority could only harry the administration with a barrage of verbiage while voting for every appropriation which the military campaigns required." The newspaper of the Whigs, the National Intelligencer of Washington, took this position. John Quincy Adams of Massachusetts, who originally voted with "the stubborn 14," later voted for war appropriations.

Abraham Lincoln of Illinois was not yet in Congress when the war began, but after his election in 1846 he had occasion to vote and speak on the war. His "spot resolutions" became famous-he challenged Polk to specify the exact spot where American blood was shed "on the American soil." But he would not try to end the war by stopping funds for men and supplies. Speaking in the House on July 27, 1848, in support of the candidacy of General Zachary Taylor for President, he said:

But, as General Taylor is, par excellence, the hero of the Mexican War, and as you Democrats say we Whigs have always opposed the war, you think it must be very awkward and embarrassing for us to go for General Taylor. The declaration that we have always opposed the war is true or false, according as one may understand the term "oppose the war." If to say "the war was unnecessarily and unconstitutionally commenced by the President" be opposing the war, then the Whigs have very generally opposed it… The marching an army into the midst of a peaceful Mexican settlement, frightening the inhabitants away, leaving their growing crops and other property to destruction, to you may appear a perfectly amiable, peaceful, unprovoking procedure; but it does not appear so to us.… But if, when the war had begun, and had become the cause of the country, the giving-of our money and our blood, in common with yours, was support of the war, then it is not true that we have always opposed the war. With few individual exceptions, you have constantly had our votes here for all the necessary supplies…

A handful of antislavery Congressmen voted against all war measures, seeing the Mexican campaign as a means of extending the southern slave territory. One of these was Joshua Giddings of Ohio, a fiery speaker, physically powerful, who called it "an aggressive, unholy, and unjust war." He explained his vote against supplying arms and men: "In the murder of Mexicans upon their own soil, or in robbing them of their country, I can take no part either now or hereafter. The guilt of these crimes must rest on others-I will not participate in them…" Giddings pointed to the British Whigs who, during the American Revolution, announced in Parliament in 1776 that they would not vote supplies for a war to oppress Americans.

After Congress acted in May of 1846, there were rallies and demonstrations for the war in New York, Baltimore, Indianapolis, Philadelphia, and many other places. Thousands rushed to volunteer for the army. The poet Walt Whitman wrote in the Brooklyn Eagle in the early days of the war: "Yes: Mexico must be thoroughly chastised!.. Let our arms now be carried with a spirit which shall teach the world that, while we are not forward for a quarrel, America knows how to crush, as well as how to expand!"

Accompanying all this aggressiveness was the idea that the United States would be giving the blessings of liberty and democracy to more people. This was intermingled with ideas of racial superiority, longings for the beautiful lands of New Mexico and California, and thoughts of commercial enterprise across the Pacific.

Speaking of California, the Illinois State Register asked: "Shall this garden of beauty be suffered to lie dormant in its wild and useless luxuriance?… myriads of enterprising Americans would flock to its rich and inviting prairies; the hum of Anglo-American industry would be heard in its valleys; cities would rise upon its plains and sea-coast, and the resources and wealth of the nation be increased in an incalculable degree." The American Review talked of Mexicans yielding to "a superior population, insensibly oozing into her territories, changing her customs, and out-living, out-trading, exterminating her weaker blood…" The New York Herald was saying, by 1847: "The universal Yankee nation can regenerate and disenthrall the people of Mexico in a few years; and we believe it is a part of our destiny to civilize that beautiful country."

A letter appeared in the New York Journal of Commerce introducing God into the situation: "The supreme Ruler of the universe seems to interpose, and aid the energy of man towards benefiting mankind. His interposition… seems to me to be identified with the success of our arms… That the redemption of 7,000,000 of souls from all the vices that infest the human race, is the ostensible object… appears manifest."

Senator H. V. Johnson said:

I believe we should be recreant to our noble mission, if we refused acquiescence in the high purposes of a wise Providence. War has its evils. In all ages it has been the minister of wholesale death and appalling desolation; but however inscrutable to us, it has also been made, by the Allwise Dispenser of events, the instrumentality of accomplishing the great end of human elevation and human happiness… It is in this view, that I subscribe to the doctrine of "manifest destiny."

The Congressional Globe of February 11, 1847, reported: