The announcement outside the statehouse came from state Sen. Murray Clark, who said he was dropping his bid for the Republican nomination to head Daniels' campaign committee.
Supporters said Clark's withdrawal gave the official start of Daniels' campaign a tremendous boost of contacts and fundraising. Clark was the running mate of gubernatorial nominee David McIntosh in 2000, when they lost to Gov. Frank O'Bannon and Lt. Gov. Joe Kernan. McIntosh is running again next year; O'Bannon cannot seek a third straight term under state law.
Daniels, whose last day as White House budget director was Friday, had long been expected to run.
Besides McIntosh, three other Republicans are seeking the gubernatorial nomination: state Sen. Luke Kenley, conservative activist Eric Miller and Petersburg Mayor Randy Harris.
Two Democrats-state Sen. Vi Simpson and former Democratic National Committee Chairman Joe Andrew-are seeking their party's nomination.