Obviously, lots of them have publicly indicated that they intend to support a certain candidate.  And lots more surely will.

But when it comes time for them to actually place their vote, is it necessarily public?

There's been a lot of talk recently along the lines of "Clinton needs 64% of the remaining delegates".  Well, she's almost certainly not going to get 64% of the remaining pledged delegates, so this got me wondering: how many more superdelegates does each candidate realistically need, at this point?

According to CBS, the current counts are the following:

Obama, pledged: 1392
Clinton, pledged: 1226

In total, there are 3253 pledged delegates.  This means that there are 635 pledged delegates who are currently unaccounted for.

Let's assume that each candidate will get roughly half (which doesn't seem like an awful assumption) - 317 or 318.  Hell, we'll give the 318 to Clinton, just to be magnanimous.

That means that at the end of the primaries, the pledged delegate count will be approximately:

Obama: 1709
Clinton: 1544

Again according to CBS, the current superdelegate counts are:

Obama: 202
Clinton: 245

Which brings us to:

Obama: 1911
Clinton: 1789

A candidate will need at least 2025 votes to wrap it up.  Which means:

Obama needs 114 more superdelegates
Clinton needs 236 more superdelegates

There are a total of 795 superdelegates, 447 of which have already expressed a preference.  Leaving 348 superdelegates currently available.

Which means:

Obama needs slightly less than one out of every three remaining superdelegates.

Clinton needs slightly more than two out of every three remaining superdelegates.