Charleston, S.C. –- Newt Gingrich climbed aboard the U.S.S. Yorktown here on the eve of the South Carolina Republican primary, fended off a heckler and declared he is the best bet for voters who want to put a conservative in the White House.

“I do not believe you can defeat Barack Obama with a Massachusetts moderate,” the former Georgia congressman said of Mitt Romney, his chief rival in the race for the GOP nomination in the Palmetto State. “I think we have to have a solid conservative who can make the case for where America has to go and who can make the case for our principles.”

Flanked by cub scouts and standing with his wife before a large U.S. flag, Gingrich spoke to hundreds of enthusiastic supporters below deck in the Yorktown, which was given its name in honor of the ship that sunk in the 1942 Battle of Midway.

A heckler in the crowd pierced the silence, shouting: “When will you release your ethics report?” It was an apparent reference to Romney’s call Friday for Gingrich to ask that officials release documents from the congressional ethics investigation into his actions in the 1990s. Gingrich quickly shot back that those records are already public.

“Actually, if you would do a little research instead of shouting mindlessly, you would discover that the entire thing is available online in the Thomas system,” Gingrich snapped. “And you can print it out. I think it is 900 pages. When you get done reading it, let me know if there are any questions.”

The crowd cheered Gingrich’s sharp response. But Gingrich wasn’t done. He next took aim at Romney’s unwillingness to immediately make his tax returns public. Gingrich made his tax returns public Thursday.

“I assume you’re for the candidate,” Gingrich told the heckler, “who is afraid to release his income taxes.”