Qualification in a democratic election is a matter of judgement by voters. Sanders thinks Clinton's history of misjudgements disqualifies her.
It's actually not his call or her call: it is the people's call.
The Democratic party is what its members want it to be. If they nominate Sanders, his policies will represent it. This would mean a move back towards the sort of position on the spectrum represented by FDR.
For myself, which means nothing, I would prefer someone to administer mostly continuity of policy - but foreign policy and education look like live issues. Getting things through Congress is going to be a challenge, but this problem may be cured by the Republicans' choice of candidate.
I also agree with Sanders that reducing the influence of incumbent wealth makes sense, although this wild election actually throws that issue into question. Bush spent oodles and got nowhere. Trump has spent little and is winning. And Sanders has raised adequate funds to compete with the Clinton money machine.
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