By credible, I meant in comparison to the Republican nominee, since Sanders is no longer available for the highest pot. If I were US citizen, I’d be torn between Stein (Green) and Clinton. I generally don’t like the idea of “career politician”, which is what you describe but the lack of unpreparedness to realities of politics (ignoring separation of judiciary from the executive, or a previously stated opinion of own running mate regarding Aleppo) and how you play the game is shocking.