WASHINGTON — Final campaign finance tallies trickled out Thursday for a presidential race expected to be the most expensive in U.S. political history, showing a last-minute $10 million contribution to a political action committee backing Republican candidate Mitt Romney from a billionaire Las Vegas casino magnate who has been the election’s biggest moneyman.

The $10 million given by Sheldon Adelson to the Restore Our Future super PAC raised the casino owner’s total contributions for the 2012 campaign to at least $72 million, all for Republicans.

The new campaign finance filings to the Federal Election Commission were among newly-released records covering the final two weeks of the race, when campaign organizations for Romney and President Barack Obama, along with a slew of super PACs, raised and spent millions toward an expected $2 billion campaign.

By late October, both campaigns already had neared $1 billion in expenditures, and super PACs supporting Obama and Romney had spent more than $500 million in media ads. Politically-oriented nonprofit “social welfare” organizations that do not have to declare their finances or identify their fundraisers have spent hundreds of millions more on issue ads.

Adelson, who owns casinos in Las Vegas, Singapore and the Chinese territory of Macau, has been the top donor in the 2012 race. He has provided more than $54 million supporting Romney and other GOP presidential candidates, and an additional $18 million for other Republicans.

The latest $10 million figure for donations from Adelson and his wife, Miriam, was released Thursday only for the pro-Romney Restore Our Future, but the couple’s totals could grow as more campaign finance tallies are reported.

Adelson vowed early in the presidential race that his political donations would top $100 million by the November election. His postelection super PAC total does not match that figure, but he hinted that he would also give millions more to GOP-leaning nonprofits that do not have to report their war chests to the FEC, but instead provide confidential figures to the Internal Revenue Service.