Yes, I agree. Some just may not go vote at all, rather than not vote for BO. A very few will vote for someone other than BO.
If they don’t show up to vote for someone other than Obama, it won’t matter - there will still be enough ballots printed and allocated for everyone who is registered, whether they show up or not. It’s the no-shows whose unclaimed ballots will be hijacked by party hacks, but the hacks’ll only be able to do it in precincts where they either control al the election judges or where the judges are known to be unobservant, lazy or easily distracted.