WASHINGTON - Republican presidential challenger Mitt Romney and his allies raised $170.5 million in September, the campaign said on Monday, falling just short of the 2012 fundraising record set last month by Democratic rival President Barack Obama.

Republicans began October with $191.2 million in cash on hand - money ready to be spent on advertising, get-out-the-vote efforts, staff, offices, rallies and other campaigning in the weeks before the November 6 election.

Obama and the Democratic National Committee already have reported raising $181 million in September, the best mark so far in the most expensive presidential election campaign in US history. They did not disclose how much they had left in cash on hand.

September was the second consecutive month in which the Democrats out raised Romney's team after three months of the Republicans leading the way in fundraising.

It was also one of the toughest months for Romney: His position weakened in the polls first as a result of the new focus shifting to the Democratic Party Convention and then to a secretly filmed video that showed him calling 47 percent of Americans who receive government funds "victims."

Romney regained footing earlier this month when he delivered a strong performance against Obama in the first presidential debate on October 3. Campaign officials said the debate kicked up donations and helped the Republican candidate gain on the incumbent in the polls just weeks ahead of Election Day.

"Americans can't afford four more years like the last four," Spencer Zwick, Romney's finance chairman, said in a statement.

"With less than one month left, we will continue the hard work of raising the resources to ensure that Mitt Romney and Paul Ryan can win in November and bring real change to the American people."

Obama has since regained a slim lead in the tight race. The Reuters/Ipsos daily tracking poll on Monday showed him at 47 percent compared with Romney's 45 percent.

"This race is tied," Obama said in an email to supporters asking for last-minute donations on Monday. "What we do over the next 22 days will determine not just the next four years, but what this country looks like for decades to come."