Rick Santorum, who is expected to launch his presidential campaign at the end of May, wrote in his 2014 book Blue Collar Conservatives that President Obama "doesn't understand America" because he was raised by a "radical family" overseas.

"President Obama doesn't understand America," the former Pennsylvania senator wrote. "Maybe that's because he was raised in a radical family, much of the time overseas, and educated by people who saw only the worst in this country. He abandoned the slogan of 'hope' a long time ago. When Obama appeals to Americans, his themes are envy, resentment, and fear. He can mobilize his base on the Left with that talk, but it falls flat with everyone else."

Santorum was writing about the problems America faced in his book and contrasting Obama with past "great leader[s]" who took on challenges.

"Though some of today's problems are new, Americans have faced serious challenges before, and we have always prevailed. Sometimes in the hour of crisis , we have been blessed with a great leader," wrote Santorum.

"Abraham Lincoln guided us through the Civil War. Franklin Roosevelt inspired us with the determination to defeat Nazism and fascism in World War II. Ronald Reagan restored our confidence after the economic, military, and political crises of the 1970s and led us to victory in the Cold War. There is no such leader in the Oval Office now, no one who can appeal to the values that make this country great because he believes in them himself."

Santorum's comments about Obama fit into a larger theme of his book. He writes that "for more than a century, the growing left wing of the Democratic Party has been pursuing a secularist and socialist agenda for America," using "class warfare" to push through their agenda.

"Their method is class warfare— pitting one group of Americans against another. It's the rich versus the poor, men versus women, the 1 percent versus the 99, the insurance company versus the uninsured, and the natural gas driller versus his neighbors. They don't want to improve on America's success, correct its mistakes, and help it live up to its promise. They think that something is wrong with America at its core—that it needs to be "fundamentally transformed."