Mississippi Governor Haley Barbour speaks during the Republican Leadership Conference in New Orleans, Louisiana June 17, 2011. REUTERS/Sean Gardner (UNITED STATES - Tags: POLITICS)

Following attacks lodged this week by Tim Pawlenty and Jon Huntsman’s campaign, the Mississippi governor and former national party chairman pleaded with his fellow Republicans to be willing to vote for someone who is not perfect.

“The nomination is wide open, so it’s gonna be a scrap,” Barbour said, adding: “Don’t get hung up on purity. … In this business, it is unity that wins elections.”

It’s not the first time that Barbour has inserted himself into the presidential race with a call for unity – expect plenty more – but it is part of an interesting dynamic that exists in the GOP primary.

While the Republican party may not have many big names in the presidential race, it does have some well-respected party elders – graybeards, if you will – to watch over the process and makes sure things don’t get out of hand.

Barbour is chief among them, but other graybeards will also be close to the process.

Other Republican graybeards who could play significant roles in guiding the process include former Florida governor Jeb Bush and Indiana Gov. Mitch Daniels. Both, like Barbour, have declined to run for president in their own right, but retain considerable influence, particularly on their pet issues – Bush on the Hispanic vote and education, and Daniels on the need for fiscal austerity.

Seeing how these non-candidates insert themselves into the process over the next six months will be very interesting. And their messages matter.

Barbour’s “play nice” message delivered Friday could be seen as particularly helpful to Mitt Romney, who has problems with social issues and the health care bill he signed as governor of Massachusetts.

But it’s bigger than that; virtually every Republican candidate has a black mark on his or her resume, whether it be support for a bailout, earmarks, cap and trade or civil unions.

Given those weaknesses, there is plenty of material with which the GOP candidates can snipe at each other. By de-emphasizing purity, Barbour is trying to temper the expectations of GOP activists and hopefully stem some of those attacks, lest a wounded nominee emerge.

“I know that I’m not going to agree with him or her on every issue, and I can tell you you’re not going to agree with him or her on every issue,” Barbour said of the eventual nominee.

It’s a familiar role for Barbour, who has long been seen as among the smartest political minds in the party. But for the other graybeards – some who may have future presidential aspirations of their own – it’s going to be a matter of just how much influence they would like to have and when they choose to exert it.

Bush and Daniels haven’t been all-that-public in recent months, but keep an eye on them, as they have the ability to affect the race ahead.