Finally finished watching this. I really don't understand why anyone would think Keane was supposed to be a proxy for Clinton when, what was shown of her beliefs, was very much unlike Clinton. Clinton's a hawk who would gladly snuggle up with the intelligence community and start some wars. And that difference is something that was apparent since episode one of the show, so it's not a rewrite issue. I hate agreeing with Tyen on anything, but if Keane wasn't a woman, I doubt anyone would draw a comparison to Clinton in any form.
Maybe if you said she was an idealized democrat, I could buy that, but even then there was barely any development of her political ideology outside of her stances toward the military and intelligence services.
That said, I too agree her behavior at the end was heavy-handed, but in terms of character development, I thought it was at least partly justified. She knew people in the intelligence service were involved in smearing her son and in her assassination (as well as the isolation earlier in the season). She puffed up as a strong person but when she was actually in mortal danger, the fear was very visible in her demeanor (good job by Marvel). I think it broke her in some way, made her unable to trust anyone outside of her close circle. It's not that unheard of -- leaders who survive assassination attempts tend to take a harder line and insulate themselves, understandably.
I do worry about next season, though. I think Homeland suffers when it tries to go for bigger and bigger storylines, ala 24. It forces the characters into ever more unbelievable situations. But, with the way they ended things, how could the focus be on anything but getting rid of Keane?
It's too bad they never recaptured what they had in that first season. There have been hints of it here and there (the first halves of S2, S4, and S5 were fairly strong, imo), but it always kind of sputters and lurches toward the end. This is a show that really does not end its seasons well, for the most part.