By Alina Selyukh and Alexander Cohen

WASHINGTON, Dec 6 (Reuters) - Mitt Romney's presidential campaign had $25.7 million left in the bank days after the Nov. 6 election that ended months of relentless fundraising in the most expensive race in U.S. history, new campaign finance disclosures showed on Thursday.

President Barack Obama, a Democrat, defeated the Republican candidate following a campaign that cost more than $2 billion overall.

Obama's re-election effort had $14.2 million left as of Nov. 26, according to the Federal Election Commission disclosures.

Leftover campaign cash is common and often goes to the national party or other candidates.

The Romney campaign on Thursday said every raised dollar had gone toward Romney's run and that it "continues to process invoices for pre-election expenses." It expected to have less than $1 million by the end of the year.

"It is not uncommon. It is of course a great risk," said Sheila Krumholz, executive director of the Center for Responsive Politics that tracks campaign finance. "As a loser you want to make sure you've given it your all."

Obama and Romney both spent much of their campaign cash on voter outreach and especially advertising. But the Democrat and his "Super PAC" backers at Priorities USA Action, an unlimited-spending group, held an early advertising game advantage.

Obama's campaign dominated the airwaves, booking the increasingly expensive spots earlier and at the lowest price.

The "super" political action committee, which was legally barred from coordinating with the campaign, ran a series of aggressive ads about Romney's private equity past that portrayed him as a corporate raider.

The damaging ads, as well as negative press surrounding Romney's disparaging "47 percent" comment about Americans relying on government funds, contributed to the candidate's defeat.

The pro-Romney Super PAC Restore Our Future - boosted once again by this year's Republican mega-donor Sheldon Adelson - plowed $45.5 million into a last-ditch effort to sway voters, according to Thursday's filings.

But according to Reuters/Ipsos polling, nearly three-quarters of Americans had made up their minds in the presidential race before Obama and Romney faced off in the first debate on Oct. 3.

The pro-Obama group spent $20.9 million from Oct. 18 and had $4.3 million in cash on hand as of Nov. 26, according to the FEC filings. Romney's Restore Our Future reported having $842,062 left.

Adelson, billionaire chief executive of Las Vegas Sands , and his wife Miriam contributed another $10 million to Restore Our Future, accounting for nearly half of all the group's last-minute fundraising and bringing the couple's total gift to the Super PAC to $30 million.

Adelson's total donations to Republican candidates and organizations, although not all of them are disclosed, are said to have topped $100 million this election cycle. He planned to spend "that much and more" in the next campaign, he told the Wall Street Journal earlier this month.

The pro-Obama Super PAC received 11th-hour $1 million infusions from two of its own top donors, media mogul Fred Eychaner and Houston lawyer Steve Mostyn. They brought Eychaner's total to $4.5 million, and Mostyn's to $3 million, according to FEC filings. (Editing by Xavier Briand)

Also on HuffPost:

Loading Slideshow...
  • 2012 -- Mitt Romney

    Republican presidential candidate, Mitt Romney, speaks at the podium as he concedes the presidency on November 7, 2012 in Boston, Massachusetts. (Photo by Matthew Cavanaugh/Getty Images)

  • 2008 -- John McCain

    Sen. John McCain, R-Ariz., gestures to his supporters, while his wife, Cindy looks on during his concession speech at the Arizona Biltmore in Phoenix, Tuesday, Nov. 4, 2008. (AP Photo/Elise Amendola)

  • 2004 -- John Kerry

    Former Democratic presidential candidate U.S. Senator John Kerry (D-MA) stands on stage with his wife Teresa Heinz Kerry after delivering his concession speech at Faneuil Hall on November 3, 2004 in Boston, Massachusetts. (Photo by Chris Hondros/Getty Images)

  • 2000 -- Al Gore

    Democratic presidental candidate Al Gore leaves the voting booth after casting his vote at Forks River Elementry School in Elmwood, Tennessee on November 7, 2000. (TIMOTHY A. CLARY/AFP/Getty Images)

  • 1996 -- Bob Dole

    Republican presidential candidate Bob Dole lowers his head while making his concession speech to supporters at a Washington hotel, on Tuesday, Nov. 5, 1996. (AP Photo/J. Scott Applewhite)

  • 1992 -- George H.W. Bush

    U.S. President George Bush concedes the election on Nov. 3, 1992 after losing to President-elect Bill Clinton. (BOB DAEMMRICH/AFP/Getty Images)

  • 1992 -- Ross Perot

    U.S. independent presidential candidate Ross Perot delivers his concession speech on November 3, 1992 after Democrat Bill Clinton won the presidential election. (Photo credit should read PAUL RICHARDS/AFP/Getty Images)

  • 1988 -- Michael Dukakis

    Democratic presidential candidate Michael Dukakis wipes his upper lip during the first presidential debate with his opponent U.S. Vice President George Bush in Winston-Salem, N.C. on Sept. 25, 1988. (AP Photo/Bob Jordan)

  • 1984 -- Walter Mondale

    Defeated presidential hopeful Walter Mondale addresses supporters at night, Tuesday, Nov. 7, 1984 at the St. Paul Civic center, conceding to President Reagan. (AP Photo/Jim Mone)

  • 1980 -- Jimmy Carter

    U.S. President Jimmy Carter concedes defeat in the presidential election as he addresses a group of Carter-Mondale supporters in Washington, D.C., on Tuesday, Nov. 4, 1980. (AP Photo/Barry Thumma)

  • 1976 -- Gerald Ford

    President Gerald Ford speaks in the White House Press Room in Washington on November 3, 1976, conceding defeat to Jimmy Carter. (AP photo/ stf)

  • 1972 -- George McGovern

    Sen. George McGovern and his family in Sioux Falls, election night, Nov. 7, 1972 after he was defeated by Richard Nixon, and conceding the election. (AP Photo)

  • 1968 -- Hubert H. Humphrey

    Vice President Hubert H. Humphrey spaks at the Alfred E. Smith memorial dinner in Waldorf Astoria on Oct. 16, 1968 in New York. (AP Photo/John Lent)

  • 1964 -- Barry Goldwater

    A contact sheet of Republican senator Barry Morris Goldwater of Arizona concedes the 1964 presidential election to President Lyndon Johnson at a press conference held at his campaign headquarters at the Camelback Inn, Phoenix, Arizona, on November 4, 1964. (Photo by Washington Bureau/Getty Images)

  • 1960 -- Richard Nixon

    Vice President Nixon points to home-made sign at airport as he arrives in home state to cast his ballot on Nov. 8, 1960 in Ontario, California. (AP Photo)

  • 1956 -- Adlai Stevenson

    Sen. John F. Kennedy of Massachusetts talks with Democratic presidential candidate Adlai Stevenson on August 12, 1956 in Chicago. (AP Photo)

  • 1952 -- Adlai Stevenson

    Movie Actress Piper Laurie (left) is wearing a donkey head beauty spot on her cheek as she chats with Gov. Adlai Stevenson of Illinois, Democratic presidential nominee in Portland on Sept. 8, 1952. (AP Photo)

  • 1948 -- Thomas Dewey

    Dewey ran as the presidential candidate of the Republican Party in the elections of 1944 and 1948. (Photo by Fox Photos/Getty Images)

  • 1944, 1948 -- Thomas Dewey

    Thomas Dewey (1902 - 1971) Governor of the State of New York broadcasting over the 'Crusade of Freedom' radio. Dewey was the presidential candidate of the Republican Party in the elections of 1944 and 1948. (Photo by Keystone/Getty Images)

  • 1940 -- Wendell Wilkie

    Wendell Willkie, rehearses a report to the nation at a New York City radio station on Oct. 26, 1942. Willkie was President Roosevelt's personal representative, and his Republican opponent in the 1940 presidential elections. (AP Photo/Murray Becker)

  • 1936 -- Alf Landon

    Gov. Alf M. Landon, G.O.P. presidential nominee, voting in Independence, Kansas on Nov. 3, 1936. (AP Photo)

  • 1932 -- Herbert Hoover

    Herbert Hoover is shown leaving Madison Square Garden, Oct. 31, 1932 in New York City, after delivering his major campaign address before a crowd estimated at 22,000. (AP Photo)

  • 1928 -- Alfred E. Smith

    Governor Alfred E. Smith speaks in New York on Nov. 2, 1928. (AP Photo)

  • 1924 -- John W. Davis

    John W. Davis, Democratic nominee for President of the U.S., and his wife, are pictured on the estate of Charles Dana Gibson at Seven Hundred Acre Island in Dark Harbor, Maine on July 21, 1924. (AP Photo)

  • 1920 -- James M. Cox

    Democratic candidates for the presidency and vice-presidency of the United States, Governor James M Cox and Franklin Delano Roosevelt (1882 - 1945) are seen at the head of a nomination parade in Dayton, Ohio on Nov. 1, 1920. (Photo by Topical Press Agency/Getty Images)

  • 1916 -- Charles Evans Hughes

  • 1912 -- Theodore Roosevelt

    Theodore Roosevelt during the progressive campaign of 1912. (AP Photo)