ANCHORAGE, Alaska (Reuters) - Alaska Lieutenant Governor Byron Mallott resigned abruptly on Tuesday in a murky scandal over admitted “inappropriate comments” as he and his running mate, Governor Bill Walker, neared the end of a tough re-election campaign.

Mallott, 75, a Democrat and the first Alaska Native elected to statewide office, had teamed up with Walker, a former Republican turned independent, to run on a unity ticket four years ago, and the two men were seeking a second term together in the Nov. 6 election.

Valerie Nurr’araaluk Davidson, also an Alaska Native and formerly the state’s health and social services commissioner, was sworn in on Tuesday to succeed Mallott, the governor’s office said in a statement.

A spokeswoman for the Walker-Mallott campaign said it was too close to the election to remove Mallott’s name from the ballot, but that if the governor prevailed in November, Davidson would step in to serve as lieutenant governor.

Walker faces a challenge from Republican former state legislator Mike Dunleavy and Democrat Mark Begich, a former U.S. senator and Anchorage mayor, in a three-way race where opinion polls show Dunleavy well in the lead.

Walker and Begich are widely seen as taking votes away from each another, and Mallott’s resignation sparked speculation among political analysts that the scandal might benefit Begich by leading Walker supporters to throw their support to the Democrat.

The genesis of the shake-up remained unclear.

Walker said he learned of “the incident” on Monday night, and accepted his running mate’s resignation with “profound disappointment and sadness.” Mallott “recently made inappropriate comments that do not reflect the sterling level of behavior required in his role as Lieutenant Governor,” his statement said.

‘RESPECT FOR WOMEN’

In a resignation letter released shortly after he stepped down, Mallott said his departure was “compelled by inappropriate comments I made that placed a person whom I respect and revere in a position of vulnerability.”

His actions had “compromised” Walker’s ability to lead, he said.

Neither the governor nor Mallott explained the nature of the comments in question.

Davidson was quoted separately as saying: “Respect for women, and the dignity of all Alaskans, is our responsibility. I stand ready to serve as your lieutenant governor.”

Neither she nor the governor took questions after delivering brief remarks to reporters.

Mallott, a Tlingit tribal member and a longtime fixture in Alaska politics and Alaska Native causes, had a close relationship with Walker, and guided the administration’s climate-change policy.

His resignation came on the eve of the annual convention of the Alaska Federation of Natives (AFN), a powerful constituency in the state. Mallott was scheduled to address the meeting.

The AFN had opposed Brett Kavanaugh’s nomination to the U.S. Supreme Court even before accusations of sexual assault became public, because of their concerns about his record on Native American rights, labor and environmental concerns.

Although a Democrat, Mallott co-chaired Lisa Murkowski’s successful 2010 write-in campaign for re-election to the U.S. Senate as an independent. Murkowski was the only member of the Senate Republican caucus who did not vote for Kavanaugh’s confirmation.