You're asking multiple questions here, that need to be disentangled.
NH's primary law specifically exempts Iowa from the 7 day window. However, you're correct that NH SoS Bill Gardner has, in the past, ignored the 7 day window provision of the law, such as in the case of Delaware in 1996.
But the thing is, Gardner's interpretation of the NH primary law isn't based on a principled assessment of "what is a primary?". His interpretation really depends on "candidate attention":
http://frontloading.blogspot.com/2011/10/on-defining-similar-contest-and.htmlIn 1996, for example, all of the candidates except Steve Forbes agreed to boycott Delaware in order to respect NH's place on the calendar. So Gardner then figured it was OK to hold the primary just four days earlier, because the candidates were going to ignore Delaware anyway.
In 2012, Nevada's status as an early caucus state was sanctioned by both of the national parties, and there's a debate being held there. A few of the candidates (most notably Romney) have already made some campaign stops there. So NH sees it as more of a threat.
The candidates then go along with a boycott because, I guess, they think NH has historically been more important in primary races, and therefore their primary must be catered to....or something. (Don't ask for logic in primary politics. The argument here is entirely circular. NH is important because the candidates make it important. Therefore, they have to respect its importance.)
They also want to peddle the story that Romney orchestrated Nevada's move to Jan. 14 (which I'm pretty sure he didn't do, but they like to believe he did).
As for why Nevada gets "blamed" for this, rather than South Carolina or Florida or Colorado and Minnesota.....from NH's perspective, it's not a matter of "blame". Nevada is the state that's in their way, so they'll try to bully it out of the way. *Why* it's in their way is beside the point.
