ORLANDO, Fla.—As President Obama has attacked Americans for Prosperity by name several times over the last month, the grassroots organization that has been heavily involved in the Tea Party movement has seen increased interest in their group.

“Literally lots have signed up,” said Tim Phillips, the president of Americans for Prosperity (AFP), while driving down a Florida interstate here on the group’s Spending Revolt bus. “Lots of folks have contributed financially because they know if the president of the United States is attacking you because you’re opposing his agenda, you’re probably doing something that’s effective.”

Obama has singled out AFP by name four times over the last month at events in Texas, Pennsylvania and Connecticut, suggesting that groups involved in the Tea Party movement are receiving funding from shady sources.

“Right now all around this country there are groups with harmless-sounding names like Americans for Prosperity, who are running millions of dollars of ads against Democratic candidates all across the country,” Obama said last month at a Democratic event in Austin. “And they don’t have to say who exactly the Americans for Prosperity are.  You don’t know if it’s a foreign-controlled corporation.  You don’t know if it’s a big oil company, or a big bank.”

Phillips called the insinuation that AFP is taking money from foreign sources “ludicrous.”

“It doesn’t make any sense. What’s he saying?” Phillips said with a laugh. “That we somehow are controlled by a foreign group?”

At a “Spending Revolt” rally at a lake in Titusville, Fla., Phillips joked about Obama’s suggestion, pointing to members of the crowd and saying, “Mr. President, come on the road with us and you can meet these foreign industries.”