WHY MCCAIN WON

From NBC's Norah O'Donnell and Adam Verdugo

How did McCain win in South Carolina, where the vast majority of voters describe themselvs as conservative? After all, this was the place where McCain's 2000 presidential bid was all but dashed because he failed to sway the party faithful. Tonight, he did very well among the Republican base, which in this contest accounted for 79% of the electorate.

More than two-thirds of those going to the polls today described themselves some shade of conservative: 34% very conservative, 34% somewhat conservative, and 24% moderate. McCain won almost half of the moderates -- 47% -- with no other candidate getting a significant share. And while Huckabee clearly did well amongst those voters who described themselves as very conservative -- 38% -- the other three candidates reigned in strong numbers as well, preventing Huckabee from dominating this group: Thompson at 21%, McCain at 19%, and Romney at 17%.

Among the 35% of voters who described themselves as "somewhat conservative," McCain edged out Huckabee 32%-30%. McCain's campaign faltered in 2000, largely because he could not appeal to conservative and core Republican voters. He made up for that tonight.

Also, military veterans made up 25% of the electorate, and of that group, McCain bested Huckabee 36%-29%. Lastly, among voters that said that experience matters the most, McCain held a 3-to-1 advantage over Romney. No one else even came close.