Supporters of the ruling Law and Justice party (PiS) attend a ceremony marking the seventh anniversary of the presidential plane crash in Smolensk, Russia in front of the presidential palace in Warsaw, on April 10, 2017. Then-Polish President Lech Kaczynski the twin brother of PiS's figurehead, Jaroslaw Kaczynski—was among those who died in the crash on April 10, 2010.