On April 8, 2014, Johnson announced she was running in the 2014 United States Senate special election in Oklahoma. Johnson faced Patrick Hayes and perennial candidate Jim Rogers. Johnson finished first in the Democratic primary with a plurality, and faced Rogers in a runoff election. Rogers had an advantage with name recognition heading into the runoff election, having appeared numerous times on the ballot in Oklahoma. Johnson, having spent 8 years in the Oklahoma State Senate as an outspoken critic of the Republican legislature, was able to acquire experienced campaign staff to secure a runoff election victory. Controversy would later surround a successful lawsuit with Johnson staff member Rico Smith. Smith filed a suit claiming Johnson did not properly pay him according to a contract signed by Johnson's campaign staff. That suit was sustained by the court. Campaign Manager Bailey Perkins, succeeded by Colletta Harper, along with Communications Director James Cooper, an Oklahoma City journalist and professor, and Political Director David Roberts, a veteran political operative and former 2008 Obama for America staff member rounded out the organizational structure. Rogers' name recognition did little to combat Johnson's growing notoriety and campaign organization. Johnson won the runoff election, defeating Rogers by 14 percentage points, to face Rep. James Lankford in the general election campaign. Johnson lost the election for the unexpired term of Tom Coburn to James Lankford, by a margin of 237,923 29.0% to Lankford's 557,002, 67.9%, with independent candidate Mark Beard collecting 25,965 votes, 3.2% of the total. Oklahoma had the lowest voter turnout in the country in the 2014 midterm elections with only 29% of registered voters casting a ballot.