Hotline’s John Mercurio wrote an excellent article on the impact of Sam Brownback’s entrance into the Presidential race. The argument comes down to two points. First:

If he can prove he’s viable, Brownback could force both Romney and Giuliani to recalibrate White House strategies that rely heavily on courting conservative critics of McCain.

And second:

"It’s always struck me that Romney would not emerge as the candidate of the most conservative elements of the party," said Jim Guth, an expert in conservative GOP politics at Furman University in South Carolina. "If Brownback does become a threat on the right, [Romney’s] move has to be to edge toward the middle and carve out a very centrist constituency. He should make some hay out of the 2006 election and say he’s a new kind of candidate who can appeal to conservatives but work on issues, like health care, across the aisle."

If that happens, Romney’s statements like:

“Just like jihadists who are attacking us economically and militarily, just like the challenge we face competitively from Asia, our culture is under attack, only this time from within,” Romney said at a fundraiser for Republican congressional candidate Mike Whalen at Thunder Bay Grille in Davenport.

Hotline’s summary of his statements at an FRC conference:

Romney classified the clash over cultural values as a major crisis on par with the jihadist threat, the emergence of Asia as a super-power, the country’s over-dependence on oil and an overweening federal government.

May make it hard for Romney to pivot back to the middle. And it could become a flip from pro-life to pro-choice to pro-life to more concilliatory. This seems hard to sustain. And that is why the recent attacks on Romney by organization’s like Rightmarch (including their nationwide newspaper ad campaign).

In essence, Brownback is going to try to "pop" in Iowa, slamming Romney for flip-flopping on social conservative issues. After that and likely losses in NH, SC would be do or die, where his Mormonism could be very difficult. (an amusing question: who gets invited to speak at Bob Jones? McCain? The pro-gay, pro-choice Catholic, Giuliani? The Mormon? Or Brownback?)

It will be interesting to see how the fight for social conservatives play out. However, two of the biggest gets in Iowa are already gotten between McCain and Brownback.