DUNN, North Carolina – Democratic presidential candidate Barack Obama raised more than $150 million for his campaign in September, breaking the record he set the previous month, his campaign said on Sunday.

Obama's prodigious fundraising has been a key in the race against Republican Sen. John McCain, allowing Obama to blanket the air waves with advertisements in the run-up to the November 4 election.

The Obama campaign said it added 632,000 new donors in September to bring the total to 3.1 million. It said the average donation for the month was less than $100.

With more than $150 million in September, Obama more than doubled the $66 million he brought in for August, which had been a record.

Unlike McCain, Obama, an Illinois senator, chose not to accept public funding for his campaign, freeing him to raise millions privately.