The Cincture of the Virgin Mary, believed by the faithful to be the belt worn by the Madonna, is said to promote fertility and good health and was brought by Greek monks to Russia last month, greeted on arrival by Prime Minister Vladimir Putin.
Putin, whose United Russia Party hopes to maintain domination of the lower house of parliament in the election on December 4, has long courted the Orthodox Church. A former KGB spy, he now portrays himself as a devout Christian.
"We have been married for nine years already, and we very much want to have a child, maybe this belt will help us," 32-year-old Irina Khilchenko said as she stood in near-freezing temperatures in front of her husband, Valery.
The couple, from Bryansk, travelled six hours by bus and had been standing close to the front of the line outside the Cathedral of Christ the Saviour for about 13 hours to wait for the relic's arrival.
More than 2 million Russians have seen the relic in the past few weeks in cities including Norilsk, Vladivostok and Yekaterinburg, said the St. Andrew the First-Called Foundation that arranged the tour.
The Foundation, chaired by the head of Russia's state railways and long-time Putin associate Vladimir Yakunin, said the relic's arrival shortly before the parliamentary election was coincidental.
"It is absolutely not related. We wanted it to come in the summer, but the entire process, the discussions, took a long time," spokesman Alexander Gatilin said.
He said the Cincture, which is usually stored at the Vatopedi Monastery on Mount Athos, had not left Greece for the past 200 years.
The arrival of the belt, with its reputed health benefits, coincides with government efforts to boost Russia's population, which has declined to 142 million since the Soviet Union broke up, threatening a demographic crisis. The Russian Orthodox Church has backed the campaign.
Pilgrims polled in the line outside the cathedral, rebuilt in the 1990s after the Soviet leadership blew it up in 1931, unanimously backed the Church's view.
"It is a great sin, for me the topic is closed," 52-year-old Kursk native Valentina Myasnyankina said, as others murmured in agreement.
Most also voiced support for the United Russia party.
"In general I think Orthodox believers will vote for the party that is closest to the Orthodox Church," said Nina Antonova, who arrived Saturday morning from Bryansk. "That party is United Russia."
The 63-year-old grandmother flashed a gold-toothed smile, and shortly thereafter the church bells rang out above the din of weekend city traffic.