Final answer:
Chester A. Arthur became president after the assassination of President James A. Garfield in 1881, succeeded Garfield as per constitutional protocol since he was the vice president, and later signed the Pendleton Civil Service Act fostering civil service reform.
Step-by-step explanation:
Chester Alan Arthur became President of the United States following the assassination of President James A. Garfield in July 1881. Arthur had been elected as Garfield's vice president, and, in accordance with the U.S. Constitution, succeeded to the presidency upon Garfield's death. Arthur's presidency began under the unfortunate circumstances of an assassin's bullet, but he took this opportunity to promote civil service reform. In 1883, he signed the Pendleton Civil Service Act, which established the Civil Service Commission and introduced a competitive exam process for certain government jobs. His actions marked a significant move away from the spoils system that had previously dominated government job appointments.
Arthur's support for the Pendleton Act and his initial association with political machines made his position within the Republican Party precarious. When the time came for the 1884 election, his support within the party had waned. The Republican Party was divided; some members formed a new faction known as the Mugwumps, and ultimately, the party chose not to nominate Arthur for the presidency. Consequently, Grover Cleveland, the Democratic candidate, won the election.
Despite his initiatives in government reform and establishing the U.S. Tariff Commission to investigate high tariffs, Arthur's influence on the Republican Party and his lackluster support among powerful political factions limited his ability to win the presidential nomination in his own right.