Steven Showers, who put up the 14-foot sign last August in front of his house in Newbury Park, Calif., was convicted of eight misdemeanor zoning code violations for the sign.
A judge had given Showers until 5 p.m. on June 26 to unplug the display, but he refused to do so during a hearing at Ventura County Superior Court on Monday.
He was then remanded to the Ventura Country Jail, until his next hearing on July 15. Bail was set at $5,000.
Last year, Showers told the Ventura County Star that he was "stunned to find out that the Mormon religion is a white supremacist, anti-black, racist ideology."
He erected his sign and created RomneysRacistHeart.com to document his legal battles with county officials.