His legal reputation gave rise to the nickname "Honest Abe"
Lincoln argued in an 1858 criminal trial, defending William "Duff" Armstrong, who was on trial for the murder of James Preston Metzker
The case is famous for Lincoln's use of a fact established by judicial notice to challenge the credibility of an eyewitness
After an opposing witness testified to seeing the crime in the moonlight, Lincoln produced a Farmers' Almanac showing the Moon was at a low angle, drastically reducing visibility
Harrison was charged with the murder of Greek Crafton who, as he lay dying of his wounds, confessed to Cartwright that he had provoked Harrison
Lincoln angrily protested the judge's initial decision to exclude Cartwright's testimony about the confession as inadmissible hearsay
Lincoln argued that the testimony involved a dying declaration and was not subject to the hearsay rule
Instead of holding Lincoln in contempt of court as expected, the judge, a Democrat, reversed his ruling and admitted the testimony into evidence, resulting in Harrison's acquittal
In his 1852 eulogy for Clay, Lincoln highlighted the latter's support for gradual emancipation and opposition to "both extremes" on the slavery issue
As the slavery debate in the Nebraska and Kansas territories became particularly acrimonious, Illinois Senator Stephen A
Douglas proposed popular sovereignty as a compromise; the measure would allow the electorate of each territory to decide the status of slavery
The legislation alarmed many Northerners, who sought to prevent the spread of slavery that could result, but Douglas's Kansas–Nebraska Act narrowly passed Congress in May 1854
Lincoln did not comment on the act until months later in his "Peoria Speech" of October 1854
Lincoln then declared his opposition to slavery, which he repeated en route to the presidency
He said the Kansas Act had a "declared indifference, but as I must think, a covert real zeal for the spread of slavery
I hate it because of the monstrous injustice of slavery itself
I hate it because it deprives our republican example of its just influence in the world...." Lincoln's attacks on the Kansas–Nebraska Act marked his return to political life
Nationally, the Whigs were irreparably split by the Kansas–Nebraska Act and other efforts to compromise on the slavery issue
Reflecting on the demise of his party, Lincoln wrote in 1855, "I think I am a Whig, but others say there are no Whigs, and that I am an abolitionist
Lincoln held out hope for rejuvenating the Whigs, though he lamented his party's growing closeness with the nativist Know Nothing movement
In 1854, Lincoln was elected to the Illinois legislature but declined to take his seat
The year's elections showed the strong opposition to the Kansas–Nebraska Act, and in the aftermath, Lincoln sought election to the United States Senate
At that time, senators were elected by the state legislature
After leading in the first six rounds of voting, he was unable to obtain a majority
Lincoln instructed his backers to vote for Lyman Trumbull
Trumbull was an antislavery Democrat, and had received few votes in the earlier ballots; his supporters, also antislavery Democrats, had vowed not to support any Whig
Lincoln's decision to withdraw enabled his Whig supporters and Trumbull's antislavery Democrats to combine and defeat the mainstream Democratic candidate, Joel Aldrich Matteson
1856 campaign 
Violent political confrontations in Kansas continued, and opposition to the Kansas–Nebraska Act remained strong throughout the North
As the 1856 elections approached, Lincoln joined the Republicans and attended the Bloomington Convention, which formally established the Illinois Republican Party
The convention platform endorsed Congress's right to regulate slavery in the territories and backed the admission of Kansas as a free state
Lincoln gave the final speech of the convention supporting the party platform and called for the preservation of the Union
At the June 1856 Republican National Convention, though Lincoln received support to run as vice president, John C
Frémont and William Dayton comprised the ticket, which Lincoln supported throughout Illinois
The Democrats nominated former Secretary of State James Buchanan and the Know-Nothings nominated former Whig President Millard Fillmore
Buchanan prevailed, while Republican William Henry Bissell won election as Governor of Illinois, and Lincoln became a leading Republican in Illinois
Sandford 
Dred Scott was a slave whose master took him from a slave state to a territory that was free as a result of the Missouri Compromise
After Scott was returned to the slave state, he petitioned a federal court for his freedom
His petition was denied in Dred Scott v
In his opinion, Supreme Court Chief Justice Roger B
Taney wrote that black people were not citizens and derived no rights from the Constitution, and that the Missouri Compromise was unconstitutional for infringing upon slave owners' "property" rights
While many Democrats hoped that Dred Scott would end the dispute over slavery in the territories, the decision sparked further outrage in the North
Lincoln denounced it as the product of a conspiracy of Democrats to support the Slave Power
Lincoln–Douglas debates and Cooper Union speech

In 1858, Douglas was up for re-election in the U.S
Senate, and Lincoln hoped to defeat him
Many in the party felt that a former Whig should be nominated in 1858, and Lincoln's 1856 campaigning and support of Trumbull had earned him a favor
Some eastern Republicans supported Douglas for his opposition to the Lecompton Constitution and admission of Kansas as a slave state
Many Illinois Republicans resented this eastern interference
For the first time, Illinois Republicans held a convention to agree upon a Senate candidate, and Lincoln won the nomination with little opposition
Lincoln accepted the nomination with great enthusiasm and zeal
After his nomination he delivered his House Divided Speech, with the biblical reference Mark 3:25, "A house divided against itself cannot stand