Newly appointed Sen. Walsh will have to fight to keep his seat in Montana

Separately, some Republicans have criticized Mr. Walsh for dysfunction in a state emergency management division he oversaw as adjutant general of the Montana National Guard. (Mr. Walsh said he had cleaned up the long-troubled agency.)

In turn, Democrats have accused Republicans of trying to “Swift-boat” Mr. Walsh, referring to the widely criticized attacks against John Kerry’s military service in Vietnam during the 2004 presidential race.

Mr. Walsh released his 378-page service record, which is filled with plaudits and commendations, among them a Bronze Star. He rejected the idea that he had used his Guard service for any personal gain. He noted that the position he had sought was unpaid and that he was interested only in pushing for better equipment and care for Montana guardsmen.

“I can look in the mirror and know that I’m doing a good job,” he said. His own campaign spots have shown him dressed in camouflage and set against a background of helicopters and armored vehicles.