Madison County, Alabama:
2012: 58.5% Romney, 40.0% Obama
2008: 56.9% McCain, 42.0% Obama
2004: 58.9% Bush, 40.2% Kerry
2000: 54.9% Bush, 42.5% Gore
Madison County, Alabama (home to Huntsville) is the type of suburban, highly educated place in the South that Clinton will have to perform well in if she hopes to put states like Mississippi and South Carolina into play. Can she win there this year? It hasn't voted for a Democrat since 1976.
I'll say that HRC actually narrowly wins Madison County this fall. I think she has good chances to win Madison, Lee and Tuscaloosa counties, at least in Alabama.
Madison will certainly trend Dem and probably swings more than any other county in the state, but doubt it would be enough to flip it entirely. High single digits is likely, with mid single digits certainly possible, but flipping it entirely would probably take something around a 12-13 point national margin.