If Hillary is nominated I quite definitely plan to pull that lever in her favour (though as Andie pointed out, it doesn't matter since I too live in a state that will vote Dem), though I find Michael and Carrol's thesis reasonable.
[WS:] But it could matter if the left were better organized and managed to arrange a vote "trading" system on a larger scale (a la "Nader-trader" in 2000). Leftists in Democrat-safe states could pull the lever for more radical candidates in exchange for votes for Democrats in swing states. This way, more radical candidates could get a noticeable political support and thus send a message, without increasing the Repug chances of winning the election. It is not prohibitively difficult to arrange this in the era of internet.
Ideally, Christofascists would do the same, which might open the door for a true multiparty system.
Wojtek