It could get even nastier for Mitt Romney
Mitt Romney's speech was fluid and scathing, boiling water poured from on high on the president.
He sounded not like a man who had won his second state in a row, but who had clinched the right to fight the general election for his party.
But of course he hasn't. Not quite yet. The old problems remain. On the one hand his margin of victory emphasises he is not the choice of his whole party. On the other, his opponents just can't come together behind a clear alternative.
Iowa's second favourite son, Rick Santorum, did badly here.
Instead in second place, Ron Paul. The Texas Congressman may be the most interesting phenomenon of this campaign, and his gleeful, impish speech extolling liberty and castigating government was a thing of freewheeling beauty in a world where so much is pre-planned, plotted and rehearsed.
Path to victory?
I am not going to write him off. Perhaps the Republican right will come together behind him in future contests. But I suspect he is too strong meat, too consistently libertarian for many conservatives. He won't go quietly, however.
Tonight's result was not pre-ordained but it was predictable. The next vote in South Carolina is anything but.
As Mitt Romney made his speech surrounded by his family I couldn't help notice the different features of two of his sons, behind his left and right shoulders.
Like representations of possible futures, one son's face shone with toothy optimism. The other's mouth was drawn in a thin, grim, determined line. Few doubt Romney is on a path to victory. But it may be stoney or smooth.
South Carolina could get very dirty. Even by the low bar of American politics the advert "King of Bain" attacking Romney is harsh.
'Politics of envy'
It accuses him of asset stripping, of ruining a dream for thousands of Americans in order to make millions of dollars for himself. When you think that it is funded by an organisation that supports another Republican candidate, Newt Gingrich, it is pretty amazing.
Mitt Romney warned against this in his victory speech.
"President Obama wants to put free enterprise on trial, and in the last few days we've seen some desperate Republicans join forces with him."
The crowd booed in agreement at that point. Romney went on: "This is such a mistake for our party and for our nation. The country already has a leader who divides us with the bitter politics of envy. We have to offer an alternative vision."
His opponents might pull their punches in future. I doubt it, though.
Already the attacks have started a debate among conservatives about whether some forms of capitalism are unacceptable or any attack on the free market is un-American.
The king of right-wing radio, Rush Limbaugh has rushed to the defence of the front-runner he so dislikes, to the distress of other conservatives.
The message - that capitalism, unfettered, red in tooth and claw, is always inherently good - may be the creed, but that doesn't mean it is the easiest sell in these times of resentment against Wall Street and the establishment.
Romney is right in one respect. The only winner is the White House, which is trying to paint him as an out-of-touch patrician who has made his pile on the backs of ordinary Americans. The longer this goes on, the longer that message has to sink in.