According to multiple news sources, billionaire ex-Mayor of New York Michael Bloomberg is seriously considering a run for President. He would probably have to make his decision by sometime in March in order to get properly registered in all the states. If he runs, he would run as an independent.
Mayor Bloomberg initially was elected as Mayor of New York as a Republican, but then became an Independent. He is pro-choice and pro-gun control, two positions that put him in conflict with many Republicans.
What appears to be his main criteria for running? One key is if Bernie Sanders defeats Hillary Clinton for the Democratic nomination. Bloomberg appears to feel he is similar enough to Hillary Clinton that, if she is running, there is no space for him.
But if Bernie Sanders wins the Democratic nomination, or appears to be on his way to doing so, and if Ted Cruz or Donald Trump (both of whom Bloomberg may view as more extreme) win the Republican nomination, then Bloomberg might run as an independent. He would probably hope to draw some more conservative Democratic and liberal Republican voters; and he would probably donate up to $1 billion of his personal fortune to run.
So it could be a real 3 person race!