The Cleveland Plain Dealer has the story, including background:

When federal agents raided Dimora’s house and office in July 2008, citizens got their first glimpse at a corruption probe that over the next 26 months would tear apart county government.
Ever since that day, Dimora, 55, and his closest friends and political allies — some innocent, others not — lived under intense scrutiny. Within a year, Dimora was pushed to the sidelines of the Democratic Party he had led for 16 years. He defiantly refused to resign as a county commissioner and challenged prosecutors to charge him or leave him and his family alone.
Early this morning, they opted for the former. Agents arrested Dimora at his Independence home and led him out in handcuffs and chains.
“I’m sickened by it,” Tim Hagan, a fellow Democrat and commissioner, said this morning after hearing of Dimora’s arrest. “It’s been a nightmare, and it’s coming to an end.”

Others arrested in the FBI swoop this morning included county judge Steven Terry and someone the Plain Dealer identifies as “union plumber Robert Rybak.”