Final answer:
President McKinley faced strong jingoism within the Republican Party as tensions rose against Spanish rule in Cuba; however, he sought peaceful solutions and only turned to Congress for a declaration of war after Spain refused an ultimatum and as hostile actions continued.
Step-by-step explanation:
As tensions were building against the Spanish rule in Cuba, President William McKinley faced strong jingoism, or aggressive nationalism within the Republican Party. This sentiment pushed for an aggressive foreign policy. The roots of this aggressive stance can partially be traced to widespread nativism at the time, which involved prizing White Americans with older family trees over more recent immigrants and rejecting outside influences in favor of their own local customs. Despite the public and internal party pressure for military intervention, McKinley sought a peaceful resolution and refrained from aggressive actions until it was deemed necessary to intervene for Cuba's independence, ultimately leading to the Spanish-American War of 1898.
Furthermore, opposition to McKinley's expansionist stance crystallized with the formation of the Anti-Imperialist League, which promoted liberty and self-determination. Despite the pressures, McKinley only asked Congress for a declaration of war after Spain refused his ultimatum to declare Cuba's independence and continued hostile actions. Congress granted authorization for military force, along with the Teller Amendment which assured that the United States would not annex Cuba.