"That's why I have taken the decision to run for the presidency of Poland."
Krzysztof Dzieciolowski, a journalist in Warsaw, told Al Jazeera that Kaczynski's decision to run could be seen in two ways.
He said: "It may not be a surprise ... but given the tremendous personal loss that he [Kaczynski] suffered - he not only lost his twin brother but also lost the president's wife - and given the fact the twins' mother is still in hospital, it's a very hard decision on a man individually.
"On the other hand, the Law and Justice party felt an incredible vacuum, and it was really difficult to imagine anybody else who could pick up the flag, as they say, and run for the presidency."
Lech Kaczynski's term was due to expire in December and the election has been brought forward to June 20 from the autumn.
"In reality, it won't be him [Jarolslaw] running, it will be his brother. His campaign team will play on sympathy for his brother," Krzysztof Bobinski, the head of the Unia & Polska Foundation, a Warsaw think-tank, said.
"Kaczynski would have a chance to win only if other candidates make mistakes. This is a difficult situation for everybody.
"This is not a normal election campaign but I think political attitudes generally have not changed among voters."
The most recent opinion polls show Bronislaw Komorowski, the acting president and candidate for the centrist governing Civic Platform, winning the presidential election.
A TNS OBOP opinion survey conducted on April 8-14 and published on Monday showed support for PiS had risen by nine per cent points to 33 per cent since March, however it still lagged behind the party of Donald Tusk, the prime minister, on 52 per cent.
Jaroslaw Kaczynski, 60, served as prime minister in 2006 to 2007 at the head of a fractious right-wing coalition that antagonised business and political elites and strained ties with the European Union, Germany and Russia.
The Kaczynski twins, who were active in the pro-democracy Solidarity movement that toppled communism in 1989, set up the PiS in 2001.
The party is conservative on social and moral issues but left-leaning on the economy, favouring more state spending and opposing privatisation.
Kaczynski keeps tight control of the PiS, which is sceptical about further European integration and opposes Poland's early adoption of the euro.
He came close to sabotaging Angela Merkel's, the German chancellor, bid to seal a deal on a new EU treaty in 2007, famously invoking the number of Poles killed by the Nazis during the second world war to press Warsaw's demand for greater voting rights.