By Gabriela Baczynska
WARSAW (Reuters) - Poland's acting president vowed on Tuesday to move swiftly to set an election date and remove uncertainty after the deaths of President Lech Kaczynski and dozens of high-ranking officials in a plane crash in Russia.
The coffin of Kaczynski's wife Maria was received by family members, top military officials and senior Catholic clergy at a somber ceremony at Warsaw airport before being driven to the presidential palace to lie in state alongside her husband.
Thousands of Poles lined the 10-km (6-mile) route to the city center, showering the hearse carrying the popular first lady with flowers in a repeat of the moving procession that brought the president's body home on Sunday.
Kaczynski, a combative nationalist known for his distrust of both the European Union and Russia, had been traveling to mark the 70th anniversary of the massacre of more than 20,000 Polish officers by Soviet secret police in the Katyn forest in western Russia when his plane went down on Saturday in thick fog.
A total of 96 people died in the crash, including Polish military commanders, top opposition figures and the central bank governor, plunging the country into mourning and bringing forward a presidential vote originally scheduled for October.
Bronislaw Komorowski, the lower house speaker and a member of Prime Minister Donald Tusk's centrist Civic Platform (PO), had been expected to easily beat Kaczynski in the election.
But popular sympathy for Kaczynski after the crash has made it harder to predict the outcome.
"The election date must be set," Komorowski told TVP Info television, promising to announce the date on Wednesday. "This must be done as soon as possible to shorten the period in which Poland is in a period of uncertainty."
TWIN BROTHER MOURNS
Legislators, religious leaders and relatives of the dead, many in tears, packed into parliament on Tuesday for a special joint session to honor the victims. Red and white flowers, the colors of the Polish flag, and photos of parliamentarians who perished were placed on their vacant seats.
The deceased president's identical twin brother Jaroslaw, who heads the right-wing opposition party Law and Justice, stood alone in the front row of the chamber as a quartet played American composer Samuel Barber's melancholy Adagio for Strings.
In Washington, U.S. President Barack Obama led attendees of a nuclear summit he is hosting in a minute of silence.
"All of us were shocked and deeply saddened by the devastating loss of President Kaczynski, the first lady and so many distinguished civilian and military leaders," he said.
"This was a loss not just for Poland but for the world," Obama added, praising the "extraordinary strength and resilience" of the Polish people throughout their history. The White House said later he would fly to Poland for the funeral.
Suddenly without a candidate for the presidency, Law and Justice must move quickly to come up with someone to challenge Komorowski in an election that, based on constitutional guidelines, seems likely to be held on May 30 or June 13.
Polish markets have been stable since the crash, with stocks and the zloty currency little changed on Tuesday after inching higher on Monday.
The muted reaction reflects in part the fact that policy in Poland is driven primarily by the government and not the president, whose powers are limited to vetoing laws and representing the country on the international stage.
QUESTIONS OVER FLIGHT
Kaczynski and his entourage were traveling in a Russian-built Tupolev aircraft when it crashed near Smolensk airport after hitting treetops on its fourth attempt to land.
Some media have speculated that Kaczynski himself may have ordered the pilot to ignore weather warnings from Russian air traffic controllers, but prosecutors have said they have no evidence to support that.
Russian officials have recovered the two cockpit voice recorders and are decoding them.
Poles have welcomed the response of Russia's leaders to the crash. Russian President Dmitry Medvedev laid flowers at a candle-lit memorial to Kaczynski in Moscow on Monday and Prime Minister Vladimir Putin personally saw off his coffin, boosting hopes for better ties between the historic foes.
Kaczynski and his wife will be buried on Sunday in the cathedral crypt at the Wawel Royal Castle in Krakow, the ancient capital and seat of Polish kings. Along with Obama, numerous other heads of state and government, including Medvedev and German Chancellor Angela Merkel, are expected to attend.
(Additional reporting by Pawel Sobczak, Kuba Jaworowski, Chris Borowski and Karolina Slowikowska in Warsaw, Stephen Brown in Rome; writing by Noah Barkin)