First Lady Michelle Obama returned from a lavish Mediterranean vacation Sunday with daughter Sasha - and was welcomed back with a firestorm of criticism.

The first lady spent the luxurious vacation shopping and sightseeing with her daughter and a few close friends on Spain's upscale Costa del Sol, in what the White House called a private trip funded mostly by the Obamas themselves. Mrs. Obama "is a private citizen, and is the mother of a daughter on a private trip. And I think I'd leave it at that," White House Press Secretary Robert Gibbs said Wednesday.

Democratic National Committee Chairman Tim Kaine came also came to the first lady's defense. "I think it's wrong to talk about the first lady's family vacation as a politician. She's a mom," he told Matt Lauer on NBC's Today Show. "I don't think you can talk about that and give it political analysis."

A White House source told the Chicago Sun Times' Lynn Sweet that the trip was made as part of a promise to a Anita Blanchard, a close friend of the Obamas whose father had recently died. After Mrs. Obama could not attend the funeral, she accepted an invitation from Blanchard to travel to Spain with their daughters.

But critics demanded to know if the taxpayers were footing the bill, and whether it was appropriate for the first lady to be lounging on a gilded foreign coast in the Ritz Carlton's luxurious Hotel Villa Padierna during an economic downturn.

The trip drew comparisons to the monarchies of old Europe - not to the average American woman that is part of Mrs. Obama's established public persona. One New York Daily News columnist called the first lady "a modern-day Marie Antoinette." "Even the Queen of England cut her budget this year by 4 million dollars. She cut her travel by over 7 million dollars," says Ben Ferguson, a host with ICON Radio. "Even the Queen's cutting back, but Michelle Obama doesn't."

Mrs. Obama and her friends reportedly paid for their hotel accommodations and food, with taxpayers footing the bill for her security detail -- something those who defended the trip said she had no control over.

The vacation is just the latest in a string of first family summer vacation plans that have resulted in more ire than R&R. The Obamas came under fire after both the first lady and the president publicly encouraged Americans to visit the Gulf - then left for a vacation in Barr Harbor, Maine, in mid-July. The family's rumored plans for a late August vacation in elite Martha's Vineyard has also been questioned. Under fire, the White House announced that the Obamas would be visiting Florida for a mini-vacation in August ahead of the expected Martha's Vineyard 10-day reprieve.

It is unclear if the vacation criticism will have an impact on her favorability rating, which recently was very good."The fact is, Michelle Obama remains enormously popular," Democratic strategist Bernard Whitman told Fox News, citing a July Gallup poll that measured the first lady's favorability rating at a healthy 66 percent."Do I wish she had taken a vacation on the Gulf Coast rather than Spain? Sure."

She's even being asked to hit the campaign trail. The first lady's popularity has spurred on Democrats in Illinois, Pennsylvania and Florida to ask the White House for her help. If the White House agrees, the move may raise questions over whether the first lady can both be seen as just a private citizen in some instances, yet then turnaround and stump for November hopefuls as a very public official.