Former President Bill Clinton bows to Presdent Barack Obama on the stage at the Democratic National Convention in Charlotte, N.C. on Sept. 5, 2012. (AP Photo/J. Scott Applewhite)

(CNSNews.com) - President Barack Obama enjoys a massive lead over Mitt Romney among registered voters who say they have no religion, according to the Gallup tracking poll of the presidential race.

In the three-week period that ended on Sept. 2, according to Gallup, Obama led Romney 69 percent to 23 percent among those who have no religion. That was exactly the same result Gallup got in the previous three-week period ending Aug. 26.

Since Gallup started publishing demographic breakouts of its tracking poll on May 6, Obama has always held a large lead among registered voters who say they have no religion. Even so, he has managed to grow that lead.

In the three week period ending May 6, Obama led Romney 63 percent to 27 percent among registered voters with no religion.

Romney leads Obama in other religious categories that Gallup tracks. He leads Obama 47 percent to 45 percent among registered votes who say they are Catholic, 54 percent to 39 percent among those who say they are Protestant or Christian, 58 percent to 35 percent among those who say they are “highly religious” and 47 percent to 45 percent among those who say they are “moderately religious.”

Among registered voters who say they are “nonreligious,” Obama holds a 62 percent to 31 percent lead—not quite as large as his 69 percent to 23 percent lead among those who say they have no religion.

In the last three presidential elections, Gallup has asked “likely voters” in its final pre-election surveys whether they attended church weekly, monthly, or seldom/never. In each of those elections, the Democratic candidate enjoyed significant majorities among likely voters who said they seldom or never attended church. In the final pre-election surveys in 2008, Obama led McCain 62 percent to 38 percent among likely voters who said they seldom or never went to church. In 2004, John Kerry led George W. Bush 60 percent to 40 percent among those voters. And, in 2000, Al Gore led Bush 51 percent to 40 percent among those voters.

By contrast, in each of those elections, the Republican candidate enjoyed a large pre-election lead among likely voters who said they attended church weekly. In 2008, McCain led Obama 55 percent to 45 percent among these voters. In 2004, Bush led Kerry 63 percent to 37 percent among these voters. And, in 2000, Bush led Gore 56 percent to 41 percent.

Obama, in 2008, was the only one of the last three Democratic candidates to hold a pre-election lead among likely voters who attend church only monthly. That year, he led McCain 51 percent to 49 percent among this group. In 2004, Bush led Kerry 55 percent to 45 percent among likely voters who said they attended church monthly. And, in 2000, Bush led Gore 51 percent to 47 percent among these voters.

Gallup's demographic numbers for registered voters are based on a three-week rolling average. In the three weeks leading up to Sept. 2, the polling firm interviewed 9,666 registered voters. 1,282 of these registered voters said they had no religion, 2,055 said they were Catholic, and 5,399 said they were Protestant or Christian. At the same time, 2,807 said they were "nonreligious," 2,504 said they were "moderately religious," and 4,225 said they were "highly religious."