President Barack Obama had issued public statements condemning the Charlie Hebdo massacre last week, he made a personal call to French President François Hollande to discuss the Islamist attack, and he stopped by the French embassy in Washington, D.C., to offer his condolences. But his absence at Sunday's historic demonstration in Paris to honor the victims of the shooting has critics questioning his diplomatic skills with the U.S.' oldest ally.

Instead of Obama or Vice President Joe Biden, the White House sent Jane Hartley, its ambassador to France. Attorney General Eric H. Holder Jr. and Deputy Secretary of Homeland Security Alejandro Mayorkas were in Paris for security meetings but did not attend. Responding to criticism, the White House conceded on Monday that it could have handled the situation more delicately. "I think it's fair to say that we should have sent someone with a higher profile" to the event, White House Press Secretary Josh Earnest said. Of the criticism, Earnest said, "We agree that we should have sent someone with a higher profile in addition to the ambassador to France."

Secretary of State John F. Kerry said he would visit Paris this week but was unable to attend the march because of his busy schedule. He called the criticism "quibbling a little bit." "But that is why I am going there on the way home, to make it crystal-clear how passionately we feel about the events that have taken place there," he said from India.

That wasn't good enough for some conservative critics of the Obama administration. Fox News host Greta Van Susteren tweeted: "This is really embarrassing - WHERE IS PRESIDENT OBAMA? Why didn't he go?" Newt Gingrich, the former speaker of the U.S. House of Representatives who ran for president in 2012, shared on Twitter: "Sad that 50 world leaders could show solidarity in Paris but President Obama refused to participate. The cowardice continues."

Hollande and some 44 foreign leaders representing Germany, Italy, Britain, Turkey, Israel and the Palestinian territories, among others, led more than a million people through the streets of Paris Sunday, forming the largest crowd in the French capital since its liberation from Nazi Germany in 1944. 

Potential presidential candidate Sen. Marco Rubi, R-Fla., said on "CBS This Morning" that it was a "mistake" not to send a higher-ranking U.S. official to the event. "I understand that when the president travels, he brings with him a security and communications package which is intense. And I understand you drop that into the middle of something like this, it could be disruptive," Rubio said. "There’s a plethora of people they could have sent. I think in hindsight I hope that they would have done it differently."

The rally was in response to last week's massacre in which at least two gunmen burst into the Charlie Hebdo office in Paris and fatally shot 12 people, including two police officers. Hollande has called it a terrorist act.