Huckabee announced his endorsement Thursday. He described Roberts as a conservative warrior and said he's fought tirelessly for lower taxes and federal government spending.
Huckabee is a former Arkansas governor who now has a talk show on cable's Fox News Channel. He ran unsuccessfully for the Republican presidential nomination in 2008 but won Kansas' caucuses.
Roberts is seeking his fourth, six-year term. Wolf is a Leawood radiologist and has the backing of national tea party groups ahead of the state's Aug. 5 primary.
Wolf spokesman Ben Hartman said Roberts won't stop his slide in the polls no matter how many endorsements he receives.