Final answer:
The Democratic Party's 1844 campaign slogan 'Fifty-four forty or fight!' related to the Oregon Territory dispute with Great Britain. President Polk embraced the slogan but negotiated the 49th parallel as the compromise boundary. The 1840 presidential election victory belonged to the Whig Party, not the Democrats.
Step-by-step explanation:
In 1844, the Democratic Party's campaign slogan was indeed tied to the dispute with Great Britain over the Oregon Territory, famously encapsulated by the phrase "Fifty-four forty or fight!" This slogan referred to the northern latitude of the Oregon Territory to which the United States laid claim. The resolve linked to this slogan showcased President James K. Polk's willingness to go to war with Great Britain over the territory. However, in reality, Polk was prepared to negotiate and eventually accepted the 49th parallel as a compromise for the Oregon boundary, appeasing the British and preventing conflict while expanding American territory westward.
William Henry Harrison's defeat over Martin Van Buren in the presidential election of 1840 was a victory for Harrison's Whig Party, not the Democratic Party, making the statement false.