Republicans allege that the Association for Community Organizations for Reform Now is engaged in rampant voter fraud, but they've offered no proof of such a systematic effort.
On Friday, the U.S. Supreme Court overruled an attempt by Republicans to challenge the validity of 200,000 voter registrations in Ohio, saying that the party lacked the standing to sue.
The Republicans had sued to force Ohio Secretary of State Jennifer Brunner, a Democrat, to provide county election officials with lists of registrants whose personal information did not exactly match Social Security or driver's license data, a step that would leave those voters vulnerable to eligibility challenges.
Kettenring said that a senior ACORN staffer in Cleveland, after appearing on television this week, got an e-mail that said she "is going to have her life ended." A female staffer in Providence, R.I., got a threatening call from someone who said words to the effect of "We know you get off work at 9," then uttered racial epithets, he said.
McClatchy is withholding the women's names because of the threats.
Separately, vandals broke into the group's Boston and Seattle offices and stole computers, Kettenring said.
Since McCain's remarks, ACORN's 87 offices across the country have received hundreds of hostile e-mails, many of them containing racial slurs, Kettenring said. "We believe that these are specifically McCain supporters" sending the messages, he said.
The e-mail to the Cleveland employee was traced to a Facebook Web page in the name of a Baltimore man. It featured a photo of a McCain-Palin sign.
Kettenring said that the bulk of the e-mails had been either "flat-out racist" or had racial overtones. Most of the group's 400 members and about 80 percent of the 13,000 voter-registration canvassers are African-American or Latino.