Defiant Kentucky county clerk Kim Davis, a long-time Democrat, has switched to the Republican Party, saying Democrats left her in the cold in her fight to defend religious freedom amid challenges posed by the Supreme Court's decision to legalise same-sex marriags.

Davis, who has tenaciously refused to issue marriage licence to same-sex couples because of her religious beliefs, announced her allegiance to the Republican Party in Washington, D.C. at the conservative Family Research Council's Value Voters Summit, according to NBC News.

"I've always been a Democrat, but the party left me," Davis said, according to Charla Bansley, spokesperson of the Liberty Counsel, which is representing Davis in her marriage licence fight.

Davis was jailed by a court in Kentucky after she refused to end her "no marriage licence" policy, becoming a heroine among some on the religious right.

Former Arkansas Gov. Mike Huckabee, a preacher running for president but who is not doing well in the polls, has defended Davis and even visited her in jail. He said it was unfair that the government would not accommodate her religious beliefs.

Texas Sen. Ted Cruz also defended Davis.

Judge David Bunning released Davis from jail last Sept. 8 but ordered her not to interfere with her deputies who were told to issue marriage licences.

Davis said the marriage licences issued by her deputies were illegal since she did not authorise them.

She also apparently changed the marriage licence form by removing her name, prompting the American Civil Liberties Union in Kentucky to file a motion with the Kentucky District Court accusing Davis of failure to comply with the court's orders that deputy clerks must issue the licences without interference from her.

Davis was elected as Rowan county clerk last fall as a Democrat, replacing her mother who served as county clerk for 37 years.

About 65 percent of the 14,000 registered voters in Rowan are Democrats.

Kentucky Democratic Gov. Steve Beshear has been refusing to support Davis despite calls for a special session of the state legislature to pass a law to exempt Davis from issuing marriage licences.

Attorney General Jack Conway, the Democratic nominee for governor, said Davis should follow the law.