Weekly Standard editor Bill Kristol says that Republican presidential nominee Mitt Romney is going to have a tough time winning if the election is a referendum on President Barack Obama's first term.

"They need to focus on the next four years," the conservative columnist told Fox News host Chris Wallace on Sunday. "If this election is just about the last four years, that's a muddy verdict."

"Bush was president during the financial meltdown, the Obama team has turned that around pretty well," he explained. "He's got to make it a referendum on the choice about the next four years, and explain what Obama would do over the next four years that would be bad for the country and what he would do would be good for the country."

Kristol added that President Barack Obama had been "rattled" on foreign policy.

"Voters are watching, turning on the TV. Embassies are being burned, there are demonstrations in Pakistan. What's going on there? Why is it happening? What can the next president do about this? Romney should answer that question," Kristol pointed out.

"If they just go back to mindlessly reminding people for the 5,000th time, 'Guess what? The economy's not great,' they will waste the next 10 days."

Watch this video from Fox News' Fox News Sunday, broadcast Sept. 23, 2012.