Sen. John McCain's (R-Ariz.) primary opponent said Friday that former Alaska Gov. Sarah Palin (R) is backing her former running mate as a political favor.

Former Rep. J.D. Hayworth, who is challenging McCain from the right, said that he has "profound policy differences" with the 2008 GOP presidential nominee.

But he added that Palin, who is a favorite of the conservative base and Tea Party movement from which he draws support, is endorsing McCain as a token of gratitude for making her the vice presidential nominee.

"We all understand the genuine human impulse of gratitude. And obviously John McCain gave Sarah Palin her entree to the national stage politically," he said on MSNBC. "But with all due respect, it's not going to be Sarah Palin from Alaska...Arizonans are going to determine who serves in the United States Senate."

Palin was a relatively unknown governor before McCain chose her as a running mate in 2008. She is speaking at a rally for McCain's campaign Friday afternoon.

The former governor's endorsement of McCain was not a foregone conclusion; McCain's and Palin's staffs reportedly sparred on the campaign trail, suggesting that the two running mates did not always get along.

But both the senator and the ex-governor have said there was not a rift between them during the campaign.

Hayworth is challenging McCain, attacking his image as a "maverick" within the GOP ranks. McCain has said he has been consistently conservative throughout his time in the Senate.

The ex-congressman expressed confidence he would win the primary and said he expects Palin to endorse him in the general election.