According to the paper's Tuesday report, Wagner -- who has also served as a state senator, assemblywoman, and gaming commissioner -- is now registered as a nonpartisan voter rather than as a Democrat.
"It’s grown so conservative and tea-party orientated and I just can't buy into that," Wagner said. "I've left the Republican Party and it's left me, at the same time."
Her action comes despite a long-time family connection to the party.
"I did it as a symbol, I guess, that I do not like the Republican Party and what they stand for today," Wagner told the paper. "I've been a Republican all my life. My dad was active [in the GOP] in the state of Maine where I was born. It was more of a moderate, liberal Republican Party."
In 1991, Wagner became the first woman in Nevada's history to be elected lieutenant governor.
A Gallup poll released earlier this month found that the proportion of Americans who identify as Republicans has fallen to 25 percent, down from a high of 34 percent in 2004.