Editing Daniel Webster (section)

===Polk administration, 1845–1849===
{{See also|Presidency of James K. Polk}}
[[File:WebsterbyLamb.jpg|thumb|right|Portrait of Daniel Webster commissioned by the Senate in 1955]]

Webster considered retiring from public office after the 1844 election, but he accepted election to the United States Senate in early 1845.{{sfn|Remini|1997|pp=599–602}} Webster sought to block the adoption of Polk's domestic policies, but Congress, controlled by Democrats, reduced tariff rates through the [[Walker tariff]] and re-established the Independent Treasury system. In May 1846, the [[Mexican–American War]] began after Congress, responding to a [[Thornton Affair|clash]] instigated by U.S. troops against the Mexican Army at the disputed Texas–Mexico border, declared war on Mexico.{{sfn|Remini|1997|pp=618–623}} During the war, Northern Whigs became increasingly split between "Conscience Whigs" like [[Charles Sumner]], who strongly favored anti-slavery policies, and "Cotton Whigs" like Webster, who emphasized good relations with Southern leaders.{{sfn|Remini|1997|pp=624–626}} Webster had been a long-standing opponent of slavery; in an 1837 speech he called slavery a "great moral, social, and political evil," and added that he would vote against "any thing that shall extend the slavery of the African race on this continent, or add other slaveholding states to the Union."{{sfn|Remini|1997|p=464}} But, unlike his more strongly anti-slavery constituents, he did not believe that Congress should interfere with slavery in the states, and he placed less emphasis on preventing the spread of slavery into the territories.{{sfn|Remini|1997|pp=664–665}} Nonetheless, because Webster opposed the acquisition of Mexican territory (with the exception of [[San Francisco]]), he voted against the [[Treaty of Guadalupe Hidalgo]], in which the United States acquired the [[Mexican Cession]].{{sfn|Remini|1997|p=646}}

General [[Zachary Taylor]]'s success in the Mexican–American War drove him to the front ranks of Whig candidates in the [[1848 U.S. presidential election]].{{sfn|Remini|1997|pp=631–632}} As Taylor held unclear political positions and had never been publicly affiliated with the Whig Party, Clay and Webster each launched their own bids for the presidency, but opposition from the Conscience Whigs badly damaged Webster's standing.{{sfn|Remini|1997|pp=637–639}} On the first ballot of the [[1848 Whig National Convention]] Webster finished a distant fourth behind Taylor, Clay, and General [[Winfield Scott]]. Taylor ultimately won the presidential nomination on the convention's fourth ballot, while [[Millard Fillmore]] of New York was selected as the party's vice presidential nominee.{{sfn|Remini|1997|pp=651–652}} After Webster declined the request of Conscience Whigs to lead a new, anti-slavery third party, Conscience Whigs and "[[Barnburners and Hunkers|Barnburner]]" Democrats launched the [[Free Soil Party]] and nominated a ticket consisting of former president Van Buren and [[Charles Francis Adams Sr.|Charles Francis Adams]]. Despite having previously stated that he would not support Taylor in the 1848 presidential campaign, Webster threw his backing behind Taylor. Ultimately, Taylor won the election, defeating both Van Buren and Democratic nominee [[Lewis Cass]].{{sfn|Remini|1997|pp=653–656}}