Final answer:
The second Republican Party emerged in the 1850s in response to the extension of slavery and the fall of the Whig Party.
Step-by-step explanation:
Following the decline of the Whig Party after the 1852 elections, the American political landscape experienced a reorientation of party structures. The second Republican Party emerged as a result of sectional issues that intensified after the Mexican-American War and the Kansas-Nebraska Act, which further inflamed the slavery debate. The Republican Party was formed by northerners who were opposed to the extension of slavery and became an amalgamation of disgruntled Democrats, disillusioned Free Soilers, distraught Whigs, and discouraged Know-Nothings.
The pivotal election of 1856 demonstrated the Republican Party's substantial support in the North, representing a regional divide that would come to define American politics in the years leading up to the Civil War. The Republican Party's establishment was a response not only to the spread of slavery but also to other key issues such as the role of the federal government and economic development. The Republicans gained momentum and eventually supplanted the Whigs as the principal opposition to the Democratic Party, marking the end of what is known as the Second Party System.
Internal disagreements within the Republican Party later led to a faction known as the Liberal Republicans, who advocated for limited government and smaller federal initiatives. Such debates and the changing political landscape signaled a shift in American political ideology during an era that saw the country grappling with rapid economic and social changes.