UPDATE: Just another jailhouse nut with a few salt packets or whatever, as the Denver Post reports:
An inmate at the Arapahoe County Jail mailed a letter that contained powder to Sen. John McCain’s campaign office in Centennial, authorities said Thursday.
A handful of campaign workers rushed to local hospitals after an envelope containing powder and a threatening letter was opened in McCain’s office.
The substance is not considered hazardous, but had not been officially identified late Thursday, said U.S. Secret Service Agent Malcolm Wiley.
The letter came from Marc Ramsey, an inmate in the jail, officials said Thursday night.
“He is a prolific writer of threatening letters,” Wiley said…
Breaking Denver Post:
The U.S. Secret Service says white powder and a threat were received at Sen. John McCain’s office in Centennial today.
“We have people responding,” said Special Agent Malcolm Wiley. “We have no reports that anyone has been hurt.”
No information was available yet on what the powder is or what form the threat came in.