PPP-National: Clinton +5

[Mr. Morden]

Trump in 4th place with blacks:

Clinton 89%
Johnson 4%
Stein 4%
Trump 2%

[Mr. Morden]

Trump in 4th place with blacks:

Clinton 89%
Johnson 4%
Stein 4%
Trump 2%

That doesn't add up to 100%, why do polls never add up to 100%?

The remaining folks are undecided.

[Mr. Morden]

Regarding the question of whether there's a missing Trump vote...since polls typically include some fraction of respondents who are undecided, don't most candidates overperform their polls?  E.g., if the polls said:

Trump 45%
Cruz 30%
Kasich 18%
Undecided 7%

and actual results were:

Trump 48%
Cruz 32%
Kasich 20%

then all three candidates beat their poll numbers, because they all got some of the undecideds (or the undecideds didn't show up).  But you wouldn’t say that the polls were undercounting anyone’s support.  Those undecideds had to go somewhere.

So my question is even post-Indiana, how much did Trump actually overperform his polling, relative to what you would expect given that he was inevitably going to get his share of the undecided vote.