Barack Obama's campaign is pulling staffers from North Dakota and sending them to Wisconsin and Minnesota, where polls show a tight race between the Democratic senator and Republican presidential candidate John McCain.

An Obama spokeswoman, Amy Brundage, won't say how many staffers are relocating, but Democratic activists put the number at more than 50.

Obama has opened 11 North Dakota campaign offices and run television advertising in the state, which is unusual for a Democratic presidential candidate.

Democrats say the Obama campaign employees have been working to identify sympathetic voters, a task that's more difficult in North Dakota because the state doesn't have voter registration.