Two non-rightwingnut experts have recently criticized PPP for exaggerating the validity of a poll in which they pitted House Republicans versus "generic" Democrats (i.e. Democrats with no name) ahead of the 2014 Congressional elections.
To summarize, PPP's credibility is low as they hyped the possibility of a Democratic House takeover in 2011 and 2012, yet this takeover did not come close to happening, as you would find out if you searched how many Republicans and Democrats exist in the House at the moment.
The link to criticism by Mark Blumenthal is here: http://www.huffingtonpost.com/...
The link to criticism by Nate Cohn of The New Republic: http://www.newrepublic.com/...
PPP has been great in Presidential elections, but if PPP again is shown to have overhyped the outcome of the next House of Representatives elections (2014), the Daily Kos should consider dropping the polling firm.
If PPP does it again, it will be the second time that Daily Kos hires a pollster which simply tells liberals/Democrats what they want to hear instead of what reality is.
We will have to wait until the day after 2014 election day in order to answer this question: For now, PPP is advised to get better at what they do.