Iranian presidential hopeful Akbar Hashemi Rafsanjani has promised economic prosperity and an easing of tensions with the outside world.
Pro-reformists are gathering behind Akbar Hashemi Rafsanjani
He made the pledge in a TV address on the eve of a vote run-off with Tehran's hardline mayor Mahmoud Ahmadinejad.
An opinion poll from the Iran student news agency, Isna, shows that the two candidates are neck and neck.
Meanwhile, 25 people have reportedly been held over alleged vote-rigging in the first round of the election.
A military figure and an intelligence officer are among those arrested, the state-run news agency IRNA reported.
In a separate development, Iranian officials confirmed that a printing press in Tehran, which had been producing pamphlets against Mr Rafsanjani, had been closed down.
Several candidates, including Mr Rafsanjani, alleged that the first round was tarnished by what they described as "organised intervention".
Priority for the poor
In his TV address, Mr Rafsanjani pledged to give Iranians billions of dollars of stock options and benefits as campaigning heated up ahead of Friday's unprecedented run-off.
He said he would give "every Iranian family 100m rials (around $11,000) in shares of state companies to be privatised".
Akbar Hashemi Rafsanjani - 21%
Mahmoud Ahmadinejad - 19.5%
Mehdi Karroubi - 17.3%
Source: Iranian interior ministry
And he promised to "prioritise the poorer classes," giving the unemployed up to 1.5m rials ($165).
Tension with the West over Iran's nuclear programme was the most urgent foreign policy issue, he said.
Tehran needs to "convince them [the West] that our programme is for peaceful purposes," he said.
But it is yet to be seen whether his appeal to the nation's reason can counter the momentum created by his hardline rival's populist approach, the BBC's Sadeq Saba in Tehran says.
Mr Ahmadinejad has pledged to fight corruption and discrimination, and his promise to redistribute wealth has struck a chord with many of Iran's poor.
In his television address a day earlier, Mr Ahmadinejad claimed the country's vast oil wealth was controlled by one powerful family - a reference to Mr Rafsanjani, who is alleged to have a substantial interest in the oil industry.
Mahmoud Ahmadinejad has won support among the poorer classes
The claim was rejected by the oil ministry.
Such rumours, although always denied by the 70-year-old cleric, have led many ordinary Iranians to lose faith in the former president and key founder of the Islamic state.
This election is seen as running along class lines, with the more liberal middle classes supporting Mr Rafsanjani and Mr Ahmadinejad hailed as a hero of the working classes.
From humble origins, Mr Ahmadinejad is unapologetically hardline and has brushed aside the idea that re-establishing ties with Washington will solve Iran's problems.
But he has dismissed concerns by moderates that he would introduce an Iranian "Taleban-style" government, with strict gender segregation and making women wear the head-to-toe chador.
"The country's true problems are unemployment and housing, not what to wear," he told state television.
He also attempted to show his liberal side by joking about how his children's use of the internet - viewed with disapproval by some religious hardliners - has landed him with high telephone bills.
Overnight, hundreds of Ahmadinejad posters sprung up around Tehran before campaigning officially ended at 0900 (0430GMT) on Thursday, Reuters news agency reported.
Some 47 million people will be eligible to vote when polls open on Friday for the first presidential election run-off ever to be held in the Islamic state.
With half of the population under the age of 25, the minimum voting age is 15.
Reformist groups have expressed fears that the vote will be rigged, following allegations of dirty tricks in the first round.
Such fears were echoed by the reformist-controlled Interior Ministry earlier in the week.