There was speculation earlier this year that the true dynamic behind the tea-bagging movement was not opposition to taxes but rather racist anger over the election of an African-American president. After all, taxes had been lowered, not raised at that point, and the only tax hikes on the table targeted people making over $250,000 per year, which was probably about five or six times the income of an average tea-bagger family of four.

The tea-bagging movement appears to have ended on July 4, when attendance at rallies was down across the country, in part because Fox News failed to promote the events 24/7 as they had for events in April.

Birthers were out in force at tea-bagger rallies from the beginning, carrying signs demanding that Pres. Obama release his birth certificate — which, of course, his campaign had done in June 2008. (To see how the connection lives on in the Intertubes, just plug keywords like “tea party,” “obama” and “birth certificate” into the Google and stand back.)

As tea bagging sputters to an end, Birtherism appears to be moving up. For example, there are a dozen or so proud Birthers in the U.S. House, including one marquee brand name, Rep. Marsha Blackburn of Tennessee, and one in the Senate, Richard Shelby of Alabama.

Now a new poll has found that Birthers are predominantly Republicans — no surprise there — and that the South leads all other regions by far as a hotbed of Birtherism.

According to the Research 2000/Daily Kos poll, 77 percent all Americans believe Pres. Obama is a citizen, while 23 percent either do not (11 percent) or aren’t sure (12 percent).

In the party split, 93 percent of Dems believe the president is a citizen, 4 percent do not and 3 percent aren’t sure. Among independents, 83 percent believe he is a citizen, 8 percent don’t and 9 percent are not sure.

However, only 42 percent of Republicans believe Pres. Obama is a citizen, 23 percent do not and 30 percent aren’t sure.

Regionally, in the Northeast, Midwest and West, roughly 90 percent believe Obama is a citizen while approximately 5 percent do not and 5 percent aren’t sure.

In the South, just 47 percent believe he is a citizen, 23 percent do not and 30 percent aren’t sure.

But does this make the Birther movement racist at its core? Not necessarily. Racism is pervasive throughout the country, even if Birtherism is less so. On the other hand, polls and reports abound these days showing the GOP is shriveling into a party of old, white Southern men. The absence of people of color in the party demographics — especially in the South, where blacks tend to be more conservative than in other parts of the country — speaks volumes.

Still, the fact that Birthers are more prevalent in the states of the old Confederacy may explain why Birthers refused to be convinced by hard evidence that includes a certificate of live birth vouchsafed by the Republican governor of Hawaii, as well as the fact that birth announcements for Barack Obama Jr. appeared in both Honolulu newspapers a day or two after his birth in August 1961.

But facts don’t matter to bigots. And this stubborn refusal to accept documentary evidence is the most convincing argument yet for the proposition that the Birther movement is a racist phenomenon at its core.