In 2013, Smitherman announced his candidacy to succeed Greg Abbott as state attorney general in the Republican primary election held on March 4, 2014, when Abbott polled 91.5 percent of the ballots cast to win the party's nomination for governor to succeed the retiring Rick Perry, who declined to seek a fourth full term. Smitherman's opponents were State Senator Ken Paxton of McKinney in Collin County and State Representative Dan Branch of Dallas County.
Smitherman finished in third place with 281,064 votes (22.1 percent) in the primary race for attorney general.
Smitherman was reared in Highlands in Harris County on the east side of Houston, Texas. He graduated from Ross S. Sterling High School in Baytown, Texas. He then received a Bachelor of Business Administration summa cum laude from Texas A&M University at College Station. Thereafter, he obtained his Juris Doctor from the University of Texas School of Law in Austin, while he worked at the state capitol for a state senator, Lindon Williams, a Democrat. Smitherman further received a Master of Public Administration degree from the John F. Kennedy School of Government at Harvard University. There he was awarded the first Joel Leff Fellowship in Political Economy.
Smitherman began a career in banking, where he held leadership positions for First Boston, Lazard, and J.P. Morgan Securities, and eventually rose to become the head of Bank One's national municipal finance group before he was fired in April 2002. Bank One's stated reason for the termination was that Smitherman had failed to get company approval before he co-authored an opinion column in the Houston Chronicle with two conservative Houston city council members, in which the authors discussed how the city could improve its credit rating. In January 2003, Smitherman became a prosecutor in the Harris County District Attorney’s office, and in May 2003 Perry named him to the board of the Texas Public Finance Authority.
In April 2004, Governor Perry named Smitherman to the Texas Public Utility Commission. He became the chairman of that body in November 2007.
After seven years at the PUC, where Smitherman was seen as an advocate of deregulation, he left in July 2011 when Perry appointed him to the Railroad Commission to fill the position vacated by Republican Michael L. Williams, an unsuccessful candidate in 2012 for the United States House of Representatives. He was elected as chairman of the commission on February 28, 2012, after the departure of Elizabeth Ames Jones to run for the state senate.
Smitherman's term expired in January 2015. He was succeeded by Ryan Sitton of Friendswood, who serves with two other Republicans, David J. Porter of Lee County, who unseated former commissioner Victor G. Carrillo in the Republican primary in 2010 but is retiring effective January 2017, and Christi Craddick of Austin, who was elected in 2012 to fill the seat formerly held by Elizabeth Ames Jones but occupied in the preceding interim months by Buddy Garcia of Austin.
In 2012, Smitherman was the Republican nominee for the two years remaining in Williams' unexpired term on the Railroad Commission. In the July 31, 2012 runoff election, Smitherman defeated his fellow conservative Greg Parker, a county commissioner in Comal County. Smitherman led with 583,022 votes (62.1 percent) to Parker's 355,245 (37.9 percent). In the first primary, Smitherman had led Parker, 44 to 28 percent but failed to win the required outright majority for nomination.
In the November 6 general election, Smitherman was elected with 4,537,625 votes (73.76%) to 1,127,074 votes (18.32%) for Libertarian Jaime Perez and 486,485 votes (7.90%) for Green Party candidate Josh Wendel; no Democrat ran for the post. Shortly after his election, he stated his support for the Sunset Advisory Commission recommendation to rename the Railroad Commission to more accurately reflect its current functions.
In the May 27, 2014 runoff election, to choose a nominee to succeed Smitherman, Ryan Sitton defeated Wayne Christian, who had been the high votegetter in the primary but held his exact same percent in the runoff and therefore lost to Sitton, an oil and gas engineer from Friendswood. Sitton also lost the District 24 legislative primary in 2012 to fellow Republican Greg Bonnen of Galveston County.
Smitherman and his wife, the former Marijane Frede, reside in Austin. They have four children, two of whom graduated from Texas A&M, one of whom is at Southern Methodist University and one is at Princeton University. The Smithermans are active members of the non-denominational Austin Ridge Church in Austin.