The body language was telling. Polish President Andrzej Duda approached Jaroslaw Kaczynski, the head of the ruling party, nodding and reaching out to shake his hand. But Kaczynski barely acknowledged him, reaching his hand to the side in a passing shake, but without pausing or even looking at the head of state.

That frosty encounter amid April 10 anniversary observances of a national tragedy has sparked rumors that a rift has emerged between the two leaders. If true, it would be the first sign of division in the ruling echelons since the conservative Law and Justice party swept to power last year, winning both the presidency and parliament — unprecedented power for any party in Poland's post-communist era.

Observers are watching the development with interest. A brief video clip of the snub has made the rounds on social media and newspapers have been discussing the relationship in recent days. If the chill is serious and lasting, it raises questions about the party's ability over the coming years to push through its conservative and nationalist program and to maintain a centralization of power that has raised concerns about the rule of law.

Political analysts say it is too early to say whether there will be real consequences to the rift and say the real test will be if Duda starts vetoing legislation passed by the parliament, where Law and Justice has a majority. Duda, who formally left the party in accordance with tradition, remains deeply loyal to the group and there is no sign he would stifle its legislative agenda.

Whatever happens, the situation is putting a renewed spotlight on a highly unusual division of power: Kaczynski holds no elected position other than that of lawmaker — by law an equal to 459 other lawmakers in the lower house of parliament. Yet he is widely acknowledged to be the most powerful person in Poland, the man calling the shots from his seat in the parliament and from his party's headquarters in Warsaw.

This arrangement results from a political calculation Kaczynski made before last year's presidential and parliamentary elections. A prime minister briefly from 2006-2007, he has a core group of loyal supporters — but also a large body of people put off by his divisive and combative style. After losing a string of elections over the previous eight years, this time he hand-picked two loyal but little-known party members to stand for the jobs of president and prime minister.

The strategy worked perfectly, bringing Duda to office followed by Beata Szydlo as prime minister, both of whom are regularly dismissed by critics as Kaczynski's "puppets."

Duda appears to be the case of a minor politician who won the country's highest office in what must have been a huge surprise even to himself — and who is showing signs after several months in office of testing his own wings.

The main point of contention between him and Kaczynski centers on the plane crash in Smolensk, Russia, in 2010, that killed Kaczynski's twin brother Lech Kaczynski and 95 others. Kaczynski supports a conspiracy theory holding that Russia might have assassinated his brother, in collusion with Polish officials in power at the time. That theory is not supported by evidence cited in official investigations, which blame the crash on crew error and dense fog.

The reluctant handshake came amid ceremonies on April 10 marking the sixth anniversary of that disaster. Duda gave a speech calling for forgiveness and reconciliation in a society deeply divided over that tragedy. Later, Kaczynski said reconciliation is only possible after those responsible are punished, an apparent rebuke of Duda's approach.

In a recent interview with the pro-government magazine w Sieci, Kaczynski tried to downplay the idea of a rift, but acknowledged their differences of opinion reflected in those speeches.

"I did not enter into polemics with the president, but I said what I thought was right," Kaczynski said. "One can treat it as a kind of a supplement, but naturally, someone could have seen a certain discrepancy."

Kaczynski appears to have snubbed Duda again just days later during celebrations marking the 1,050th anniversary of Christianity in Poland. Photos of the event appear to show a moment in which those gathered stand up as Duda arrives — with Kaczynski staying seated.

Duda's spokesman, Marek Magierowski, declined to say what the president's position is on the rift.

An increasingly independent Duda could, in theory, prove one of the greatest threats to Kaczynski, who is on a self-declared mission to remake Poland, asserting national sovereignty at the expense of the European Union, restoring traditional Catholic values and rooting out liberal and, to his mind, persisting communist influences.

Kaczynski acknowledged having some influence on Szydlo, describing her government as part of an "experiment" that will be assessed toward the end of the year — a hint he could replace her eventually.

But he would be essentially powerless to replace Duda, who was directly elected in a national vote to a five-year term ending in 2020.

"We have a situation, which I respect, that the president wants to be independent," Kaczynski said in the interview. "Probably these stories saying he might be dependent on someone are very painful to him; his entourage must be taking it very hard."

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Associated Press writer Monika Scislowska contributed to this report.