With Haslam's overwhelming victory, the Republican Party controls the governor's office and the entire state Legislature for the first time since the post-Civil War Reconstruction Era, the Knoxville Sentinel reported.
The state's congressional delegation shifted from 5-4 in favor of the Democrats to 7-2 in favor of the Republicans, The (Nashville) Tennessean reported.
"This is a history-making night for the state of Tennessee," U.S. Rep. Marsha Blackburn, who was re-elected in the 7th District, told supporters in Nashville.
Both gubernatorial candidates were relative political novices. Haslam worked for Pilot Corp., his family's gas station, convenience store and truck stop company, before running for mayor in 2003, while McWherter was making his first bid for elective office.
Haslam won a three-way Republican primary against two more conservative opponents.
Outgoing Democratic Gov. Phil Bredesen called Haslam "a man of honesty and integrity" after the results were in.
Rep. Lincoln Davis, a Democrat who has held the 4th District in middle and east Tennessee since 2003, was beaten by Dr. Scott DesJarlais.
DesJarlais was helped by a large cash infusion late in the race from the national party.
Two Republicans, state Sen. Diane Black and Stephen Fincher, a farmer, were elected in the 6th and 8th Districts. Both districts are now represented by Democrats who decided not to seek re-election.