Democrat John Gregg has been trying for months to paint Republican Mike Pence as an extremist, and his latest ad is the most direct attack in the governor's race to date.

The ad, launched this week, uses back-to-back sound bites to tie Pence to Republican Senate candidate Richard Mourdock, the Tea Party and Mourdock’s recent comment that "even when life begins in that horrible situation of rape, that it is something God intended to happen.” Unlike Gregg's earlier ads, which featured Gregg in his hometown of Sandborn, this one relies on the traditional negative ad voice-over.

Some Republicans have distanced themselves from Mourdock since he made his controversial remark last month. But political observers doubt Gregg's ad will help the former speaker of the Indiana House narrow the lead held by Pence, a congressman from Columbus.

“It’s a marginal benefit at best for him,” said Mike Wolf, associate professor of political science at Indiana University-Purdue University in Fort Wayne. “He’s got a lot of ground to make up. He’s running against a national figure, and that’s very difficult.”

Pence has said that unlike Mourdock, he believes his anti-abortion stance allows for an exception for rape. He also called for Mourdock to apologize.

"I think it was very clear I disagreed with his statement," Pence said last week. "I encouraged him to apologize. He's apologized and clarified his statement, and I think Hoosiers want us to move on."

Mourdock apologized that his comments were misconstrued after his opponent, Joe Donnelly, claimed that Mourdock said God condones rape. But Mourdock has not apologized for his pro-life stance, which is similar to Donnelly's. Last year, in fact, Donnelly backed a measure that would have denied federal abortion funding even in cases of rape and incest.

As Gregg’s ad points out, Pence has continued campaigning for Mourdock.

The ad is scheduled to air on WISH-TV Channel 8 and WRTV-TV Channel 6 through Election Day. Gregg’s campaign wanted voters to know that Pence is part of the Congressional Tea Party Caucus, spokesman Daniel Altman said.

“This is what a desperate campaign does when they have no ideas,” Pence spokeswoman Christy Denault said.

Independent polls have shown Pence leading by double digits, but the Gregg campaign last week released an internal poll claiming that he's within six points. The leading independent poll for Indiana, the Howey/DePauw poll, is due out Friday.

Gregg seemed to score points on the Tea Party and extremism in the second gubernatorial debate, before Mourdock’s rape comment, Wolf noted, and he continued the momentum in the third debate.

“It’s awfully late in the fight to be winning your first rounds,” said John Krull, director of the Franklin College Pulliam School of Journalism and opinion writer for the Statehouse File.

The image Pence has crafted makes Gregg’s attacks ineffective, even if the race were close, said Margie Hershey, Indiana University professor of political science.

Pence may agree with Mourdock on many issues, but he emphasizes family, faith and a close “fit” to Indiana, which makes him appear more moderate, Hershey said. “Pence’s personal style makes him more difficult to brand as an extremist.”