[56] Even as his professional life improved, however, Arthur and his wife experienced a personal tragedy as their only child, William, died suddenly that year at the age of two.[57] The couple took their son's death hard, and when they had another son, Chester Alan Jr., in 1864, they lavished attention on him.[58] They also had a daughter, Ellen, in 1871.[59] Both children survived to adulthood.[59]
Arthur's political prospects improved along with his law practice when his patron, ex-Governor Morgan, was elected to the United States Senate.[60] He was hired by Thomas Murphy, a Republican politician, but also a friend of William M. Tweed, the boss of the Tammany Hall Democratic organization. Murphy was also a hatter who sold goods to the Union Army, and Arthur represented him in Washington. The two became associates within New York Republican party circles, eventually rising in the ranks of the conservative branch of the party dominated by Thurlow Weed.[60] In the presidential election of 1864, Arthur and Murphy raised funds from Republicans in New York, and they attended the second inauguration of Abraham Lincoln in 1865.