So the two questions that come to mind are:

1) Who are they?

2) Who are "they" looking to take away votes from?

If Bloomberg is the pick, he'll draw down votes from Republicans more than Democrats, helping Obama's chance to be re-elected.

But if "they" are a group that do not wish to have Obama in again (as The Ulsterman Report suggests) a candidate who would suck away votes from Obama would make more sense.

If you look at third party candidates from the past, the main person hurt is the incumbent.