I don't think anyone has managed to pull this off, simply because social media is also a very effective way of broadcasting the fact that someone is trying to do so. People get pissed off when they think someone is trying to pull a fast one on them, and they feel smart when they think they've outwitted them, and both of those things make for effective viral content. This even happens when the claim isn't true; for instance, there's a perennial viral news hoax about the Washington Post running opposite headlines in Trump-supporting and Clinton-supporting areas that keeps popping up despite having a Snopes debunking.

If the social media networks clamp down on ordinary people's ability to spread political messages this might work. Which I guess could happen, given the pressure for them to do so.

(The Trump campaign seems to have sensibly not even tried this and just used micro-targetting as a way of reducing the cost of getting their message in front of the people who're interested in it. If people outside the target group saw their message organically, well, that was basically just free advertising.)

Is there any example of this? In American politics and British politics (where much of the current drama stems from), the issues and candidates are promising opposite things in many ways.

Hillary Clinton was not promising the return of coal jobs. Donald Trump was not promising a path to citizenship for illegal immigrants. Jeremy Corbyn was not promising leaving the EU.

These were all very polarized issues and perspectives.

Yes in theory you can promise to be all things to all people but microtargeting is not happening in a vacuum, and it's unlikely that politicians will have success with promising contradicting binary things.