Donors and fundraisers

Romney's financial operation has relied heavily on large checks written by wealthy supporters, in contrast to the Obama campaign, which has been aggressively courting such donors as well but relies mostly on smaller contributions.

The Romney campaign said it received more than 1 million donations in September in checks of less than $250, which were responsible for a total of $43.2 million.

Of all the cash received, 93 percent of all donations were of $250 or less, the campaign said. That means some $127 million was raised through less than 7 percent of the donations.

The Romney campaign continued to court large donors this week as some of the most influential of them gathered at a luxury hotel in Manhattan for a three-day "fall retreat" that started Monday.

The gathering was expected to include "special guests" including former New York Mayor Rudy Giuliani, real estate magnate and reality TV star Donald Trump, and Oklahoma oilman and Continental Resources CEO Harold Hamm.

Others expected to attend include Charles Schwab Corp

CEO Charles Schwab and Jimmy John's sandwich franchise CEO Jimmy John Liautaud, according to an invitation posted by the Sunlight Foundation, a nonpartisan group that seeks more transparency in campaign finance.

The major fundraisers and donors were scheduled to attend election strategy meetings with top Romney campaign staff and mingle with vice presidential candidate Paul Ryan.

Romney had originally planned to join in, but changed plans on Monday to prepare for the second presidential debate against Obama on Tuesday night at New York's Hofstra University.

Obama's campaign, which holds the all-time fundraising record for its 2008 efforts, said it held its last fundraising event last week. In 2008, Obama's campaign and the DNC together brought in $193 million in September and came close to raising $1 billion overall.