"Unbelievable," Palin said earlier this week after Obama rewrote the U.S. nuclear strategy, and she suggested the president was weak on nuclear defense.
Obama, in Prague to sign a nuclear reduction treaty with Russia, countered by deriding the former Alaska governor who resigned midway through her first term as "not much of an expert" on nuclear issues.
Palin then shot back Friday during a speech to the Southern Republican Leadership Conference in New Orleans with a reference to Obama's early career choice. Mocking the president, she dismissed "all the vast nuclear experience that he acquired as a community organizer."
Playing out over several days and across the globe, the spat foreshadowed what the country could see come the next presidential race should Palin run for president and win the GOP nomination.
The 2008 vice presidential nominee is among roughly a dozen Republicans weighing candidacies. It's a wide-open field but Republican insiders say Palin would be a serious contender if she got in the race. She is beloved by tea party activists. She's a political celebrity who draws tons of media coverage. And she has an ability to raise big money. But she's also polarizing, and there's no evidence that she can broaden her base of support beyond conservatives to win the GOP nomination, much less to beat a popular Democratic president.
Nevertheless, Palin is leaving the door open to a candidacy and has spent the past few months pummeling Obama in speeches, interviews and online. She used her speech in New Orleans to blister the president repeatedly, as did several of her potential rivals who also spoke at the three-day event.
But Obama rarely if ever responds directly to Palin. The president typically doesn't counter criticism from Republicans weighing whether to challenge him. Doing so always has the potential to elevate a rival.
The spat began Wednesday when Palin criticized Obama's rewriting of the U.S. nuclear defense policy. Her comments came during an interview on Fox News, where she is a paid analyst. She likened Obama to a kid poised for a playground fight who said, "Go ahead, punch me in the face and I'm not going to retaliate. Go ahead and do what you want to with me."
Palin was particularly incensed about the policy that says if a non-nuclear state were to use chemical or biological weapons against the U.S. or its allies, it would face a potentially devastating conventional military strike by the U.S., but not a nuclear one.
"No administration in America's history would, I think, ever have considered such a step that we just found out President Obama is supporting today," Palin said.
Across the globe in Prague, Obama was asked by ABC News to respond to the criticism.
"I really have no response," the president said. "Because last I checked, Sarah Palin's not much of an expert on nuclear issues."