Kaczynski's twin closes in on his brother's old job

He is a cat-loving, conservative bachelor who is renowned for opposing abortion, gay rights and the European Union. Yet Jaroslaw Kaczynski could emerge as Poland's new president tomorrow in an election in which he is aiming to replace his twin brother, who died in April's devastating air crash.

The controversial Mr Kaczynski says he has a moral obligation to step into the shoes of his late brother Lech, who was killed along with 95 other senior political, military and religious figures in Poland's worst ever air disaster on 10 April, when a plane carrying their party crashed in fog in western Russia.

"It is my duty to carry on for those who died – especially for my brother," Mr Kaczynski said, as he reminded supporters that he used to telephone his brother at least twice a day.

Polls suggest that the once-unpopular, 61-year-old, former Law and Justice party prime minister is trailing less than six points behind Bronislaw Komorowski, 58, the front runner and presidential candidate for the liberal Civic Platform party of Poland's Prime Minister, Donald Tusk.

There are several other candidates in the race. But if neither of the two leaders wins more than half the votes on Sunday, the contest will enter a second round on 4 July. Political observers say a second vote could boost Mr Kaczynski's chances because it could rally Poland's conservative Catholic farmers, who are his traditional supporters. They point out that many younger, liberal voters will be off on holiday by 4 July.

Yesterday Mr Kaczynski, who has been riding a wave of public sympathy since the air crash, used his last day of campaigning – which also happened to be his birthday – to visit his brother's tomb in Poland's historic Wawel castle, the resting place of Polish saints and kings. "This is a very sad birthday for me," he told journalists. Polish newspapers have dubbed him the "solemn martyr".

Yet apart from the sympathy derived from the air disaster, Mr Kacyznski has narrowed Mr Komorowski's lead by moderating his previously abrasive anti-gay and anti-EU stance and by championing the advantages of a welfare state which his opponents want to prune.

In a vigorous campaign he has been touring the country appealing for an end to internal political feuding and an improvement in Poland's relations with its erstwhile enemies Germany and Russia. "The Polish-Polish war must end," he told supporters recently; he also insisted that a " good relationship" with the country's neighbours was vital.

Mr Komorowksi, who like Mr Kaczynski was a member of the banned Solidarity trade union during Poland's communist era, is campaigning on a pro-Euro ticket and aims to see his country introducing the single currency within in the next five to six years. He has also promised to bring home the 2,600 Polish troops stationed in Afghanistan.