You're taking a gamble by going back and asking for more money. If you go back and say, "i'm sorry, I can't take less than $27", they may simply revoke the offer on the spot. Or, they may come back and counter offer with maybe $24. If you do go back and ask for more, I'd stick to the actual range that they intended to pay: $26.
So, you have to ask yourself which is more important at this stage: being employed, or matching your previous earnings. If being employed is more important, you'd be well off to suck it up, take the job, then start looking for a new one and this time grow a spine and ask for what you are worth. If however you have the luxury of not taking the job (someone else supporting you), then by all means go back and tell them something along the lines of, "I'm sorry, but I am going to need $26/hour." Offer no explanation as to why, just be polite but direct.