Current TV correspondent David Shuster says that it should not be a surprise to Republican presidential candidate Rick Santorum or anyone else that Fox News is "shilling" for former Massachusetts governor Mitt Romney.

Last week, Santorum complained to Fox News host Brian Kilmeade that the conservative news network was in the tank for Romney.

“He has Fox News shilling for him every day,” the former Pennsylvania senator explained. “No offense, Brian, but I see it.”

Shuster told CNN's Howard Kurtz on Sunday that it only makes sense because "Mitt Romney is the Republican establishment candidate and... Fox News is the Republican establishment."

"It used to be that Fox News worked for the Republican Party," the Current TV correspondent observed. "Now the Republican Party works for Fox News."

"Fox News is convinced that Mitt Romney has a better chance at beating Barack Obama than Rick Santorum or Newt Gingrich," he added. "So, they decided, 'Look, Mitt Romney is going to be the guy and we think he's the one to make it the best competitive election.' And I think, therefore, the coverage naturally becomes more pro-Mitt Romney."

Daily Caller contributor Matt Lewis contended that there was "no conspiracy" because some of Romney's toughest interviews had come from Fox News anchors Bret Baier and Megyn Kelly.

"Fox folks are predisposed to favor Mitt Romney because -- I think David's right -- they tend to be establishment," he explained. "It's not a conspiracy."

In an interview on Thursday, Romney dismissed the idea that Fox News was backing his campaign.

"I don’t think you are shilling for anyone to tell you the truth," the candidate told Kilmeade.

“I think it’s, as you say, pretty fair and balanced,” Romney insisted. “The truth is you report it all and you give us a chance to respond. That’s all we can ask for.”

Watch this video from CNN's Reliable Source, uploaded March 18, 2012.