Let's say the Spanish "did their duty," as Senator Hannah hoped, and Theodore Roosevelt was killed during the Spanish-American War.
With V.P. Garrett Hobart dead, Sec. of State John Sherman in failing health, Sec. of War Russell Alger disgraced & AG Joseph MvcKenna taking a Supreme Court spot, the 1900 choice for a running mate comes down to Philander C. Knox or Admiral George Dewey.
Celebrity has its value and the GOP wins with a McKinley-Dewey ticket. In Sept. 1901, Dewey inherits the White House.
Beginning with the 1904 election, how will this alter things?