By Yereth Rosen

ANCHORAGE, Alaska (Reuters) - Republican Senate candidate Joe Miller lost a crucial battle on Friday in his legal challenge to the write-in re-election victory claimed by incumbent Alaska Senator Lisa Murkowski.

An Alaska state Superior Court judge ruled against Miller in his lawsuit contesting 8,159 votes counted for Murkowski that he argued were entered on ballots incorrectly.

The decision moves Murkowski one step closer to winning re-election to the U.S. Senate and becoming the first high-profile politician to win a write-in campaign in more than 50 years.

A member of one of the state's most powerful political families and a senator since 2002, Murkowski had to campaign to get voters to write in her name on the ballot after Miller, endorsed by former Alaska Governor Sarah Palin and the conservative, anti-tax Tea Party movement, defeated her in Alaska's Republican primary in August.

Miller's suit claimed that Alaska's Division of Elections violated state law by adhering to "voter-intent" guidelines that accepted write-ins as valid even if they had minor misspellings, improper punctuation or handwriting mistakes.

Superior Court Judge William Carey rejected the argument that write-in ballots must be flawless to count. He issued a stay on his ruling, giving Miller until Tuesday to file an appeal with the state Supreme Court.

Late Friday, Miller issued a statement saying he was considering an appeal.

Murkowski claimed victory last month after a final ballot count by state officials gave her a 10,000-vote lead over Miller.

A federal judge issued an injunction blocking official certification of the results pending the outcome of Miller's lawsuit. The ballot is the last of the November 2 congressional elections to be decided. The outcome does not alter the makeup of the Senate, where Republicans picked up six seats. Democrats retained their majority in the Senate.

(Editing by Bill Rigby and Stacey Joyce)