Now I get it.

The reason for Trump and the birther business is to give Obama a fundraising gift.

Obama should thank Trump!

With T-shirt, Obama camp raising money off birth certificate controversy

By Shawna Thomas, Domenico Montanaro, and Mark Murray

The Obama reelection campaign is raising money off of the controversy surrounding President Obama's birth certificate.

The Obama reelection campaign is selling a T-shirt (above) to anyone who donates at least $25.

With a donation of at least $25 to the Obama campaign, donors can get a long-form birth certificate T-shirt.

The "limited edition" T-shirt on the front proclaims, "Made in America" beneath a picture of the president. On the back, is a picture of the long-form birth certificate. 

The president released his long-form birth certificate on April 27, trying to put an end to the conspiracy theory that he was not born in the United States. (For the record, again, the president was born in Hawaii.) Obama trumpeted the release of the birth certificate in a video that accompanied is stand-up routine at the White House Correspondents' Dinner.

In 2008, the Obama campaign often used merchandise as a way to raise money/build its donor base. After all, anyone who donates $25 for this shirt is a potential donor who can give more money during the election cycle.