But Nebraska voters are notoriously unpredictable. Fischer was elected after defeating two better-known Republican candidates in the 2012 primary and beating former Democratic U.S. Sen. Bob Kerrey in the general election. And despite Nebraska's heavily Republican leanings, voters have shown some willingness to elect conservative Democrats to statewide office.
Although he began his political career as a Democrat, Johanns has made a name for himself as a staunch conservative since his election to the Senate in 2008.
In his first year in the Senate, Johanns voted with the GOP 94 percent of the time, including opposing the confirmation of Supreme Court Justice Sonia Sotomayor. He opposed the 2010 health care reform law championed by President Barack Obama, calling it bad policy even after the U.S. Supreme Court in 2012 upheld it as constitutional.
But unlike many Republicans, including Fischer, Johanns publicly backed former U.S. Sen. Chuck Hagel for secretary of defense.
In 2012, when it was revealed that the Environmental Protection Agency was using aerial surveillance to check farms in the Midwest for violations of federal clean water regulations, Johanns introduced an amendment to a multifaceted farm bill to stop the flights, but it fell four votes short of the 60 needed.
He began his foray into politics nearly three decades ago, when he was elected as a Democrat to the Lancaster County Board of Supervisors in southeast Nebraska. He switched parties in 1988, winning election as a Republican to the Lincoln City Council and, three years later, the city's mayor.
His political status - and conservative leanings - have only grown since. He was elected Nebraska's governor in 1998, and during his second term accepted Bush's appointment to U.S. secretary of agriculture. He stepped down in 2007 to launch his U.S. Senate bid.
During his tenure in the Senate, Johanns has eschewed earmarks, legislative amendments that allow members of Congress to add money for local projects to national bills in a process that is often obscured from public scrutiny.
Johanns faced a health scare during his first year as a senator, undergoing surgery in March 2009 after doctors found a spot on his left lung. No cancer was found, but doctors removed the lower left lobe of his lung as a precaution. Johanns was a smoker, but quit more than 20 years ago.
"Mike Johanns epitomized principled leadership during his near three decades of public service, always putting the needs of Nebraskans first," said U.S. Sen. Jerry Moran of Kansas, the chairman of the National Republican Senatorial Committee. "I thank him for his service and wish (him) and his family the very best in their next chapter. The Cornhusker state will look to continue its strong conservative tradition by electing an equally dedicated Republican leader in 2014."