We are seeing failure of trust in to EU because its terrible at PR. Its successes are taken as local governments successes ("our govt is awesome, it snatched the money from those bureaucrats for new architecture!") which failures are easily blamed on Brussels ("We wanted to rescure our failing Shipyards and coal mining, but Brussels tells us we can't because its unfair competition! In meantime French and Germans have no issues like that! This is unfair competition and favorism of west-dominated Union!").
Then you have usual of their weird decisions that are brought as example of overgrown bureaucracy without attempt to understand the reasoning behind it. "Hey, did you hear? Idiots in Brussels decided that snails are fish, what an idiots" the popular saying goes, meantime nobody cares that such decision saved EU from making up separate legislature for seafood farming and trade.
Then we have refugee crisis which is generally something considered result of poor decisions beind done in western EU side that it is trying shift the blame on across all of the union. The situation where in Poland is explictly named amongst the countries that show no solidarity while at same time we've accepted one million people from UA doesn't help neither.
With all of this going on, its easy for populist guys to gain widespread support. However situation in Poland where traditionalistic-populistic gov gained enough of majority to rule on its own is (IMHO) primarily the result of weak opposition, whose entire idea and programme was "we are saner than those other folk" but instead we've got liberal party apparently become traditionalist one with leaks after leaks of them doing disappointing deals with each other or private business. This effectively sank primary opposition party in polls.
They've also made some harsh steps to improve the grim future of our social security system via bumping retirement age as well as forcefully relocating bulk of private savings to the public fund.
http://www.reuters.com/article/poland-pensions-idUSL6N0H02UV...
Apparently there's trend in the polls going on for few weeks now giving them growing support, but its most likely the wave of popular disgust for current gov, which would be story from 2006 repeating itself. I'm unsure if they are capable of fixing things.