The poll needs to be of likely Primary voters. Mitt could be losing for all we know.
With respect to NH, polling independents makes sense, because it's an open primary. I know some independents; they are hard-working, honest people. They tend to be a little populist, however. They do not like bailouts, subsidies, and crony capitalism. That's why they fell for McCain and his "maverick" crap. If the Pubbies nominate someone who sells out to enemies of America, like Rick Perry, they will lose these people.