Casino mogul Sheldon Adelson has given $5 million to an independent committee supporting GOP presidential aspirant Newt Gingrich, the first of what is expected to be many millions the Las Vegas billionaire plans to spend this election year.

The check from Adelson is the latest in an avalanche of campaign cash flooding the presidential season to independent groups known as Super PACs The check was cut on Friday to Winning Our Future, a group run by former Gingrich associates, according to two people close to the donor.

A person close to Adelson said that the billionaire planned to spend at least another $5 million during the campaign — either to the Gingrich-linked group or to the winner of the Republican nomination for president — and that the initial check was intended to keep Gingrich competitive in the Jan. 21 South Carolina primary.

A spokesman for Adelson said in an e-mail, “At this time I’m going to decline to comment.” Rick Tyler, a spokesman for the PAC, said, “I am not commenting on any donations at this time.” Under the law, the Gingrich campaign is not supposed to be notified of such donations because the PAC is independent.

One person close to Adelson said that more money could go to the Super PAC depending on “how Newt does in the South Carolina primary, which is presumed to be Newt’s last stand.” Until the past week, Gingrich had been leading in polls in South Carolina, but the most recent surveys have put former Massachusetts governor Mitt Romney ahead in the Palmetto State.

Last month, Politico reported that Adelson told people he planned to write a $20 million check to the group. Adelson and his spokesman denied the report. A longtime Republican donor, Adelson is limited by campaign laws on how much he can give directly to a candidate’s campaign. He and his wife have already given the maximum allowed, $2,500 each.

The couple met Gingrich in the mid-1990s and were introduced by George Harris, who was working for Adelson at the time as he was battling labor unions and government regulation in the construction and opening of the massive Venetian casino and hotel complex. The two hit it off immediately, Harris said.

Adelson is a strong supporter of Israel and his views dovetail with Gingrich on Israel and the Palestinian conflicts. Adelson is worth more than $21 billion, according to Forbes magazine and most of the Las Vegas Sands operating profit comes from Asia, with casinos in Singapore and Macau, China.

Increasingly, Super PACs have played a crucial role in this election year. Campaign finance specialists have criticized the groups as launching a new flood of secret and unlimited cash. Most of them file reports disclosing donors monthly and some file quarterly. The next reporting deadline for most will be after the primaries in New Hampshire, South Carolina and Florida.

Romney has benefited most significantly from a Super PAC known as Restore Our Future, which is staffed by former Romney advisers. That PAC helped him fend off a last-minute surge by Gingrich in Iowa. Meanwhile, Romney’s campaign spent relatively little ad money in Iowa, where he won the caucuses by eight votes.

Winning Our Future, the pro-Gingrich Super PAC, has spent $800,000 on ads, Federal Election Commission records show. Gingrich criticized Romney on Tuesday for his connections to Restore Our Future.

The Super PACs are possible because federal court rulings, including the Supreme Court’s Citizens United case in 2010, said that limits on corporate and union spending in elections were unconstitutional. The groups are forbidden from coordinating with campaigns, though several are run by political operatives who have previously worked with this year’s presidential candidates.

In the 2000s, Adelson had been the biggest supporter of Gingrich’s nonprofit political operation, American Solutions for Winning the Future, the organization that funded Gingrich’s political activities when he did not hold office. Adelson launched the group in 2006 with a $1 million donation.

American Solutions, which disintegrated this summer in Gingrich’s absence, raised and spent $52 million and provided some of the money that allowed the former speaker to travel by private jet and hired limousine.

The group spent $6.6 million on private air travel for Gingrich purchased through Moby Dick Airways, accounting for nearly 13 percent of the group’s budget, records show.