Final answer:
Business interests and humanitarian concerns were the main pressures on the President to go to war with Spain. Business interests sought economic opportunities, while humanitarian organizations aimed to aid Cuban independence due to Spain's inhumane tactics, aligned with promoting the Monroe Doctrine. Anti-imperialist groups objected to U.S. imperialism due to the war's moral and human costs.
Step-by-step explanation:
The pressures to go to war with Spain came from various groups for different reasons. Notably, business interests were in favor of the war seeking economic opportunities related to Cuban agriculture and trade expansions. Contrary to isolationist or anti-imperialist groups, which generally opposed war achieving peace or resisting territorial expansion, it was the humanitarian concerns over the treatment of Cubans and strategic considerations in line with the Monroe Doctrine that swayed public and political opinion. The Spanish used brutal tactics against Cuban rebels, prompting a humanitarian outcry. The Monroe Doctrine indicated America's claim to authority in the Western Hemisphere, which supporting Cuban independence would reinforce. President McKinley was ultimately convinced to intervene by the convergence of humanitarian and business interests, highlighted by his implementation of 'gunboat diplomacy' before a formal declaration of war.
Anti-imperialist groups, however, objected to the United States' engagement in imperialism, arguing that the human costs and moral implications did not justify the political and military actions taken under the guise of freeing Cubans. These concerns intensified with the U.S. presence in the Philippines post-Spanish surrender, fearing the establishment of an American colony aimed at opening trade in China.