I don't think Romney's doomed in NH if he loses IA. People are overestimating the importance of IA momentum on NH. The two states combined tend to provide a big momentum boost for the winners going into the states that follow, but NH frequently goes the opposite way from IA (2004 notwithstanding). And to the extent that Romney takes a hit in NH for only finishing second in IA, Giuliani could take an equally big hit in for only finishing *third* in IA.
Which leaves open the question of whether McCain takes an even larger hit for placing fifth in IA.
In the end, there are five realistic scenarios for IA/NH outcomes. With Michigan getting pushed back, these results (& the likely Romney win in WY) are the only ones before NV/SC on the 19th.
I: Romney wins both IA & NH.
Romney gains a lot of momentum, likely goes onto win NV & SC. Nomination is by no means guaranteed...Giuliani might still be in a position to win FL & do reasonably well on Super Tuesday...but Romney definitely favored.
II: Romney wins IA, but Giuliani wins NH.
Probable slight boost to Romney overall nationally (despite the unexpected NH loss). It probably won't be enough to give Romney the nomination though. SC would still be very much in the air--especially if Huckabee places a reasonably close second in IA and gets a boost therefrom. Giuliani most likely wins NV. The overall edge is Giuliani's by default--and he likely clinches the nomination if he wins SC.
III: Huckabee wins IA, but Romney wins NH.
One of the stranger scenarios--Huckabee gets a huge boost, Romney a smaller one. Should McCain finish third in NH, he's completely dead in the water. Should he finish second, it doesn't help him much but severely cripples Giuliani (who has presumably placed third in both IA & NH). Romney is slightly favored in SC, but only just. After that...who knows. The race is between two candidates who, between them, are polling no more than 25% of the vote nationwide. Likely to be very unpredictable & exciting.
IV: Huckabee wins IA, but Giuliani wins NH.
Romney is dead in the water, creating a Giuliani v. Huckabee race. Giuliani has the obvious advantage, but SC could prove volatile.
V: Huckabee wins IA, but McCain wins NH.
Romney is crippled--very unlikely that he comes back to win SC or NV after this. If he placed third in NH, he's completely dead. Giuliani is still in the game due to his overall national levels of support--although those could crumble quite quickly. Huckabee most likely has the edge in this one--but, yet again, this comes down to SC.
In III, IV, or V, should Huckabee not win the nomination, he's guaranteed the VP if he wants it. He also makes himself the automatic frontrunner in 2012 (urgh).