WARSAW (Reuters) - Poland’s ruling Law and Justice (PiS) party marked on Tuesday the end of monthly rallies commemorating the 2010 plane crash that killed President Lech Kaczynski, hoping to ease social tensions before a series of elections.

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The marches became an opportunity for PiS to fan emotions that drive many of its conservative supporters: distrust of foreigners, patriotism infused with Catholic piety and anger that Poland’s economic success is not more evenly shared.

But opposition critics accused PiS of using them to foment divisions in Poland and the party, whose opinion poll ratings haven fallen sharply, decided that Tuesday’s official gathering on the eighth anniversary of the disaster would be the last.

“We want Poles to be united, but united around good, not evil. We want a strong Poland, a just Poland, a Poland which is being listened to,” PiS leader Jaroslaw Kaczynski, Lech’s twin, told supporters in Warsaw during a ceremony to unveil a monument to the victims.

The crash in thick fog near the Russian city of Smolensk shook Poland to the core: the 96 dead included top army brass, the central bank chief and lawmakers from across the political spectrum, as well as Lech Kaczynski, a PiS founder.

At the time Jaroslaw Kaczynski accused the then prime minister Donald Tusk - a centrist who is now European Council president - of being indirectly responsible for the crash, caused, in his view, at least partially by government negligence.

Since PiS came to power in 2015, Kaczynski’s eurosceptic message has resonated with many voters, despite international accusations that the party is moving towards authoritarianism.

But its support has eroded in recent weeks amid a public outcry over financial bonuses for the government, protests over plans to tighten abortion rules and a clash with the United States and Israel over Holocaust remembrance.

Hundreds of police have guarded the marches in recent months, with sections of a main Warsaw thoroughfare closed off, and public spending on protection quadrupled as liberal activists staged counter-protests.

PiS also appears to have slowed efforts to find evidence of Russian meddling in the crash, something Kaczynski has suggested in the past, even though a government investigation into the tragedy had returned pilot error as its cause.

The party is trying to rally support before local elections this year, a European Parliament vote next spring and parliamentary elections later in 2019, followed by a presidential poll in 2020.

“The (rallies) make PiS appear divisive,” said Anna Materska-Sosnowska, a political scientist at Warsaw University. “They’ve become grotesque.”