Is a Presidential candidate suppose to tweet like that? Anyhow I hope he still wins. For safeguarding of the constitution apolitical figure or a member of the opposition needs to be the President.
I don't think any opposition party chooses her except JMM which is not part of NDA that too because of ongoing cash siezed case from one of his PA .. rest who all are supported where part of NDA as far as i know
In addition to this the opposition parties ruled states where BJP is not the main opposition would have anyway supported NDA partly because BJP is not their enemy no. 1 and closeness to center will get lot of things done which would be difficult otherwise and secondly Congress is proving time and again that it is not a serious political party and has no hopes of making a comeback unless BJP goes on a series of self goals.