Final answer:
The Whig party's split in 1852 was primarily due to disagreements over slavery, which had become an increasingly contentious issue following territorial expansion and legislation like the Compromise of 1850. The correct answer is option b.
Step-by-step explanation:
The fatal split in the Whig party in 1852 occurred over the issue of slavery. This divisive issue came to the forefront following the acquisition of new territories after the Mexican-American War and the debate over the extension of slavery into these areas. As tensions heightened, the Compromise of 1850, which aimed to solve the sectional disputes, fell short of maintaining unity within the Whig Party. The tension over the Fugitive Slave Law and the Kansas-Nebraska Act further exacerbated sectional conflicts. With the Whig Party's stance on manifest destiny and territorial expansion being linked closely to the future of slavery, they found their membership deeply divided. Consequently, after the election of 1852, the Whig Party ceased to exist as a national party.
Notable developments during this period include the Compromise of 1850, the publication of Uncle Tom's Cabin, and increasing public policy disputes influenced by the slavery issue. Ultimately, the division within the Whig Party reflected the growing national divide over slavery, which was part of the wider sectional tensions that would lead to the Civil War.