persuading them that PIS is the only factor which is able to remove the threat
That is no longer true about PiS. After bending over backwards to please the EU, in vain hope of receiving the reconstruction funds, they lost all their credibility. I already told you - that's the beginning of the end for PiS.
Solidarna Polska and, to some extent, Konfederacja are the only remaining patriotic forces in Polish politics. However, in the case of Konfederacja we would have to investigate the possbile Russian connection, so actually we are left with only Solidarna Polska (and maybe Prawica Rzeczypospolitej). Sad times for Poland. :(