Donald Trump is reviving memories of Bill Clinton's affair with a White House intern and his turbulent interactions with black voters during South Carolina's 2008 primary as the ex-president campaigns for his wife in New Hampshire.

Trump's latest broadsides on the Clintons a potential preview of a nasty, personal general election appear beneficial to both as they seek to energise voters leading into the first primary contests. But, some observers warn, they could pose a long-term risk for Trump in his effort to succeed President Barack Obama.

"If Hillary thinks she can unleash her husband, with his terrible record of women abuse, while playing the women's card on me, she's wrong!" Trump said on Twitter on Monday to his nearly 5.5 million followers.

"Remember that Bill Clinton was brought in to help Hillary against Obama in 2008. He was terrible, failed badly, and was called a racist!" he added late Monday night.

The attacks are the latest in an escalating feud between Trump and Hillary Clinton, who have been spending more time focused on each other as the first nominating contests draw nearer. Both are leading preference polls nationally though Trump appears increasingly vulnerable in Iowa, while Clinton faces a challenge from Vermont Sen. Bernie Sanders in New Hampshire.

In taking on Bill Clinton, Trump is drawing upon two longstanding Republican critiques against the former president that have received scant attention thus far: the ex-president's affair with White House intern Monica Lewinsky during the 1990s and his dust-up with black voters during the 2008 South Carolina primary.

After Obama's win, the former president noted that Jesse Jackson had won South Carolina's primary in 1984 and 1988 victories that didn't lead to the Democratic nomination. The remarks angered many black voters and officials in the state, who viewed it as an attempt to diminish Obama, then Hillary Clinton's main rival.

In a phone interview with NBC's Today Show, Trump said Tuesday that his comments about Bill Clinton were "fair game" after Hillary Clinton accused him of having a "penchant for sexism." Her remark was in response to Trump saying Clinton had been "schlonged" by Obama in the 2008 nominating contest. "There was certainly a lot of abuse of women," Trump said. He added: "And that certainly will be fair game. Certainly if they play the woman's card with respect to me, that will be fair game."



He also said he doesn't personally believe Bill Clinton is a racist and was simply recounting what was said about the ex-president at the time.