Matthew Carpenter was unexpectedly thrust into the presidency. That year in 1874 a special election would be held and it would reset the pattern of elections permanently. One important thing that happened was the passage of the 14th Amendment during his term.
Matthew Carpenter expected to receive the nomination. However, he was upstaged by famed Civil War general Ulysses S Grant who secured the Republican nomination. However, Ulysses S Grant chose Carpenter as his running mate.
The Democrats chose George McClellan, also a major general from the Civil War.
The Republicans were still heros in the North for abolishing slavery, and emphasized that reconstruction was still underway. The 14th and 15th Amendments had yet to pass. This early in the war Texas, Mississippi, and South Carolina were still under military governments and did not participate in the elections. The Democrats unsuccessfully tried to pin the economic woes on the Republicans. Ulysesses S Grant won the election.