It is not only Sanders supporters who are a bit happy to see the polls narrowing; as Clinton fan I am too.
Of course the Sanders side sees it as raising the chances that they can pull off what their narrative needs - an even razor thin win in Ohio and preferably also a win in Missouri. Then no matter how much more in the hole they go delegate-wise, no matter how insurmountable that deficit becomes end of day, they can weave the story as “We won almost as many states today as Clinton did and won Ohio. Ohio is a bellwether and is a must win in the general. Florida? Just another southern state. Yeah she wins in the South.”
I see the narrowed polls as helping reduce the chances of spinning anything less than that as a “beating of expectations” and thus a “win” even if all were lost and the delegate count deficit goes well south of 300. If polls had kept up saying expect big Hillary wins such would the card played. Now that they are narrowed moderately thin Clinton wins in all but Missouri, with a solid Clinton Florida victory and the consequent major delegate pot the day brings can at worst be spun as “Clinton trounces in Florida and ekes out most of the rest of states closing in on a 300 pledged delegate lead.”
Yes I am nervous that the polls might still be off and that Sanders can pull off Ohio in addition to Missouri and maybe even Illinois albeit all narrowly. I know that the end of day delegate result with a solid Clinton win is roughly the same with narrow wins vs narrow losses and I am not worried at all about her losing the nomination. I do become increasingly anxious about a protracted battle weakening her for the general.