The claims of fraud are debunked in a detailed report on the Michigan Civil Rights website.
An excellent article in the Wall Street Journal describes the tactics that the communist front-group BAMN used to pressure and intimidate signers of the petition. Mainstream media reports continue to ignore the background of this extremist group in their reports.
The article is well worth reading in its entirety. Here is an excerpt.
So the group launched an "investigation." They systematically called and personally visited blacks who'd signed the petition. In some cities, they had friendly talk show hosts read the names of black signers over the radio. In all cases BAMN's message was the same: How could you, a black person, sign a petition to roll back affirmative action?
BAMN's high-pressure tactics worked. Some signers and even gatherers decided they'd been deceived. In some cases they recalled being told that the petition was to "support affirmative action" and to help get their "children into college." Using pre-printed affidavits (some "signed" over the phone), BAMN collected statements from dozens of individuals and started a legal campaign to get the referendum pulled.