Susan Davis reports on the presidential race.

John McCain’s presidential campaign has been on the attack against the Association of Community Organizations for Reform Now for its voter registration tactics as well as its ties to rival Barack Obama. Today, Acorn fired back at McCain, accusing the Arizona senator of erratic and misleading behavior.

“ACORN to McCain: Have You Lost That Loving Feeling?” reads a release by the organization this afternoon, noting that McCain was the keynote speaker at a Feb. 20, 2006 Miami rally cosponsored by Acorn to build support for a comprehensive immigration reform bill co-sponsored by McCain and Sen. Edward Kennedy of Massachusetts. The bill never passed Congress.

In a statement, Bertha Lewis, chief organizer of Acorn, sharply attacked McCain, suggesting the 72-year-old senator is “erratic”—a word that Republicans believe Democratic opponents use against McCain to stir up concerns about his age.

“Maybe it is out of desperation that Sen. McCain has forgotten that he was for Acorn before he was against Acorn; he was for immigration reform before he was against immigration reform; and he was a maverick before he became erratic,” Lewis said.

She added, “We are surprised at his efforts to vilify an organization that, until recently, he saw as an ally. Maybe this surprise attack and change of heart is indicative of his state of mind, and the way he would govern.”

On Friday, McCain’s campaign called for an investigation into Obama’s ties to Acorn. The campaign has also released a Web video tying Obama to the group. The Obama campaign has said any charges of impropriety are false. However, Acorn has come under scrutiny in several states for its voter registration efforts.

The Democratic-leaning outfit has registered 1.3 million voters for the 2008 election—its best year ever–but it has also come under scrutiny in several key battleground states, including Ohio, Nevada, and Missouri, for alleged fraudulent voter schemes. “We need a full and complete and thorough investigation of these allegations which seem to be widespread,” McCain said last week.

In July, The Wall Street Journal reported on Acorn’s political activity and how they benefited from the housing bill the Democratic-controlled Congress approved earlier this year.