Casino mogul Sheldon Adelson gave $1 million in a late effort to unseat Sen. Debbie Stabenow, D-Mich.(Photo: Nicholas Kamm, AFP/Getty Images)

Story Highlights

• Sheldon Adelson aided Romney, Republican candidates across the country
• Oracle CEO Larry Ellison joined executives giving last-minute money to help Mitt Romney
• A month after election, some super PAC donations remain cloaked in secrecy

12:45AM EST December 7. 2012 - WASHINGTON -- Billionaire casino executive Sheldon Adelson, the biggest political donor of the 2012 elections, continued to pump millions of dollars into failed efforts to elect Republicans to the White House and Congress in the campaign's waning days, reports filed Thursday show.

On Oct 19, Adelson and his wife, Miriam, donated $10 million to Restore Our Future, a super PAC aiding Republican Mitt Romney's unsuccessful campaign. That day, the Las Vegas Sands CEO also pumped $1 million into a last-minute bid to unseat Democratic Sen. Debbie Stabenow of Michigan, according to the group's filings with the Federal Election Commission.

Adelson's donation accounted for more than 80% of the money that flowed to the Hardworking Americans Committee, which blasted Stabenow with television commercials in the final weeks of the campaign. Stabenow went on to trounce Republican Peter Hoekstra on Election Day, winning the state by more than 20 percentage points. The group also funded more than $140,000 in telephone calls to turn out voters for Romney in Michigan.

The committee was among dozens of outside political groups that scrambled to shape presidential and congressional races in the final weeks before the elections but were not required to disclose their donors until Thursday – the day post-election reports are due to the Federal Election Commission.

The flurry of filings highlight Adelson's 11th-hour involvement in other congressional contests. For instance, he donated $2.5 million in the final weeks of the elections to a super PAC attacking Democrat Tim Kaine, Virginia's former governor. Kaine won Virginia's U.S. Senate race.

In all, Adelson and his wife gave more than $68 million to super PACs in the 2012 elections, according to reports filed through early Thursday evening. In a recent Wall Street Journal interview, Adelson said he intended to increase his political spending in the future, despite Republican losses.

The Las Vegas-based mogul visited Washington this week, making stops on Capitol Hill to visit with Republican congressional leaders and party officials. The main purpose of the trip was to accompany his wife, who attended meetings related to her role at the U.S. Holocaust Museum, Adelson spokesman Ron Reese said.

Miriam Adelson was named to the museum's council in 2007 by President George W. Bush.

Reese declined to discuss details of Adelson's schedule and would not comment on his last-minute political spending.

The final election reports to the FEC also show:

• Restore Our Future spent a $45.5 million in the final weeks of the campaign. In addition to the Adelsons, other late donors included Oracle CEO Larry Ellison, who donated $3 million in late October, and former Price is Right host Bob Barker, who gave $174,200. Pittsburgh billionaire Richard Mellon Scaife, a newspaper publisher and longtime donor to conservative causes, donated more than $400,000 in October.
• The sources of money to several super PACs still remain cloaked in mystery. The Government Integrity Fund Action Network, which spent $2.4 million to help Romney and Republicans running for Congress in Ohio and Connecticut, took in $1.4 million from its nonprofit arm in the final three weeks of the campaign. The nonprofit does not have to disclose its funders.
• The rise of boutique super PACs, funded by one or two wealthy individuals. New York City Mayor Michael Bloomberg was the sole backer of his Independence USA PAC, pumping nearly $10 million into the group in the final weeks of the campaign to support candidates who agree with his positions on gun control, climate change and gay rights. His biggest investment: $3 million to run ads targeting the environmental record of Rep. Joe Baca, D-Calif. Baca lost to a fellow Democrat, state Sen. Gloria Negrete McLeod.
• The Democratic-aligned Patriot Majority super PAC, which mounted ran anti-Romney commercials, got virtually all of its final $405,000 haul from four large labor unions, including the AFL-CIO and United Steelworkers.

Contributing: Christopher Schnaars