The South Carolina Republican presidential primary has developed an unfortunate reputation for dirty tricks and ugly smear campaigns. The legend, alas, continues.

Twelve years ago, John McCain, fresh off a big win in New Hampshire, ran into some scurrilous attacks in the Palmetto State, where George W. Bush supporters accused McCain of having gone crazy during his imprisonment in Vietnam, McCain’s wife of being a drug addict, and McCain’s adopted daughter from Bangladesh of being a black child McCain had fathered out of wedlock. Bush won by about 11 points.

Yesterday, it was Newt Gingrich who was targeted with a smear campaign in South Carolina, the day before the primary.

Two separate e-mails sent to Republicans here claimed that Mr. Gingrich, a former House speaker, had pressured his second wife, Marianne, to terminate a pregnancy.

One of the e-mails purported to come from Mr. Gingrich’s own campaign press office and contained a fabricated quote from the speaker admitting the allegations.

Disguised as a press release, the message carried the headline: “Newt Gingrich Responds to Abortion Allegations.” … Another e-mail that went to South Carolina Republicans on Friday was made to look like a CNN breaking-news alert. It also made the claim that Mr. Gingrich had pushed his wife into terminating her pregnancy.

The allegations are false, but the fact that they were made at all — the day before voting began, when there’s less time to respond to the lies — suggests some relatively influential party insiders are worried about a predicted Gingrich victory.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.