Tehran, Iran -- In a last stand of street rallies, Iran's pro-reform groups roared back into the presidential race Wednesday with their most potent weapon: warnings that victory for an Islamic ultraconservative will erase years of hard-won social and economic gains.

The messages were driven home in demonstrations on the last day of campaigning as activists sought to turn out every vote. "Religious fascism is coming!" they shouted.

"We should not be frozen in the past," read a huge banner for Ayatollah Hashemi Rafsanjani, a self-styled progressive who has become a rallying point for liberals in Friday's runoff election.

The alliance forming behind the 70-year-old Rafsanjani -- from student dissidents to business executives -- is not so much about his policies or personal appeal. It stems more from fear of his opponent: Tehran's hard-line mayor, Mahmoud Ahmadinejad, and the momentum of his surprise No. 2 finish in last week's first round of polling.

Rafsanjani was left shaken with the challenger right on his heels, 21 percent to about 19.5 percent.

He had threatened to withdraw from the runoff after the man who placed third alleged the Revolutionary Guards intimidated voters in Ahmadinejad's favor, a close Rafsanjani aide, Mohammad Atrianfar, told The Associated Press. Rafsanjani backed down after receiving assurances from supreme leader Aytatollah Ali Khamenei that hard-liners would not manipulate the vote.

Interior Ministry spokesman Jahanbakhsh Khanjani said Tuesday that "some institutions and individuals," whom he did not identify, had violated the election laws. He did not elaborate.

The swing votes Friday will come from those whose candidates trailed in the first round.

"We cannot let extremism win," reformist Mostafa Moin, the fifth-place finisher, said after throwing his support behind Rafsanjani, who served as president in 1989-97.

The third-place finisher in the first round, former parliament speaker Mahdi Karroubi, urged citizens to flock to the polls to save Iran from "Talibanization."

Ahmadinejad has not clarified his intentions, but aides insist he is not a "Taliban-style" foe of the many social changes in Iran since the late 1990s: dating, foreign music and movies, Internet access and colorful head scarves for women.

His critics are nowhere near convinced.

Ahmadinejad is depicted as ready to dismantle the lifestyle reforms and go even further. Business groups worry he could scare off foreign investment and possibly close the Tehran Stock Exchange because Islamic codes forbid wagering. As mayor, he imposed sex-segregated elevators in municipal buildings.

Many of Rafsanjani's former rivals have been forced into a coalition of convenience.

Rafsanjani "is the lesser of two evils," said Mohammad Reza Khatami, brother of the outgoing president, Mohammad Khatami, who succeeded Rafsanjani and helped bring about sweeping reforms in Iranian society.

But President Khatami was unable to weaken the hold of the non-elected theocracy, which can overrule both the president and parliament.

The ruling clerics appear solidly behind the 49-year-old Ahmadinejad. He also counts on support from the Revolutionary Guards, the paramilitary "basiji" vigilantes and many lower-income voters inspired by his humble style.

"Finally, someone from our class has appeared," said Hamzeh Kargar, a night watchman at a Tehran apartment complex. "I will vote for him again."

The pro-Rafsanjani rallies on Wednesday -- the final official day of campaigning -- tried to win over Ahmadinejad's supporters.

"We can't go backward! Vote Rafsanjani! Please, you must vote!" a group of marchers cried in a Tehran park.

President Khatami urged a strong voter turnout -- a thinly veiled call to support Rafsanjani.

Newspapers were packed with large ads for Rafsanjani, including one from 18 music companies that paid homage to the Beatles, saying: "Let it be!"

Ahmadinejad continued his low-key campaign of fliers and modest advertising. He scheduled no major appearances Wednesday. His hard-line supporters staged small gatherings in Tehran.

In a bid to tone down political passions, the hard-line judiciary issued an order prohibiting voters from sending mobile phone text messages criticizing either candidate. It did not give details on how it might enforce the ban.

However, late Tuesday, judiciary agents seized more than 500,000 pro-Rafsanjani cards urging voters to turn back "terror and repression," the managing director the printing house, Mahmoud Reza Bahmanpour, told AP.