Pollsters always run risks when asking a lot of questions about which respondents may know little or nothing. While this is especially true with IVR (interactive voice response - automated telephone polls, with questions recorded and answers given by touch-tone), which is what PPP does, it's also the case with live-interviewer phone surveys.
There are two main risks: The respondent gets annoyed or frustrated or for some other reason feels compelled to hang up ("break off") rather than complete the poll, potentially leaving a sample that is biased in some way because those who complete the poll aren't representative of the surveyed population; and/or, if the respondent feels sufficiently invested (for whatever reason) in completing the poll, as time goes on s/he may "satisfice" and give whatever the easiest/quickest answer may be to any question, without giving it a lot of thought. (In a political poll it seems clear to me that many partisans will simply pick whoever their party's candidate is in any trial heat - more on that in a minute.)
As an aside, outside of the political polling realm, I confronted this respondent-burden problem in a survey I project-managed for the Pew Forum on Religion & Public Life in 2010, measuring Americans' religious knowledge. We ended up with a total of 32 religious knowledge questions. A Pew Forum FAQ
addressed the breakoff issue: