MONTPELIER — Ed Flanagan, the former Vermont auditor of accounts and state senator credited as the first openly gay lawmaker in the country elected to statewide office, died Friday at a nursing home in New Hampshire. He was 66.

Vermont state Representative Mary Sullivan, a Democrat who had been friends with Mr. Flanagan for decades, said Saturday she had planned to visit Flanagan on Friday but arrived shortly after his death.

Mr. Flanagan suffered a traumatic brain injury in a 2005 car crash that left him in a coma for several weeks. Sullivan said Mr. Flanagan’s declining health in recent years was a result of those injuries.

‘‘He was passionate and very progressive,’’ said Sullivan, who managed Mr. Flanagan’s unsuccessful run for Vermont attorney general in 1988. ‘‘He was guided by a moral compass.’’

Mr. Flanagan was first elected auditor in 1992. He was elected to three additional two-year terms, including two after he came out as gay in 1995.

In 2000, after leaving the auditor’s post, Mr. Flanagan ran unsuccessfully for the US Senate seat then held by Republican James Jeffords. He was elected to the state Senate in 2004. He was reelected in 2006, after he was injured in the car crash, and again in 2008.