What if disgruntled office seeker Charles Guiteau would have shot and killed U.S. Secretary of State James G. Blaine along with President Garfield? (Considering that Blaine was the one who personally rejected Guiteau's pleas for a government job, this doesn't appear to be particularly implausible.)
Who would the Republicans nominate in 1884 in this TL? Also, would the Republicans' 1884 nominee in this TL defeat Grover Cleveland that November?
Also, if so, how does U.S. history develop since that point in time?