I would refine your scale slightly to recognize the issues. On social issues, I would put the typical voter at -20 to -30. On economic issues, -10 and on defense/terror issues +10 to +20. The typical voter wants the President to take care of the economy, protect the country, and stay out his or her personal life.
Frankly the more excited the FR becomes about a candidate, the more likely the moderate independents become nervous. I don't like it but I think that is the current state of the electorate.