National advocacy groups — and a few high-profile donors, including a Las Vegas-based casino company — helped fuel the closing weeks of Maryland’s same-sex marriage campaign, new disclosure reports show.

All told, supporters raised more than twice as much money as opponents for the successful effort to uphold the state’s gay nuptials law, which takes effect Jan. 1.

Marylanders for Marriage Equality reported raising a total of $5.2 million for the campaign on Question 6, while the Maryland Marriage Alliance, which opposes the law, said it raised about $2.4 million.

But the final weeks of the race were far more competitive as both sides spent money as quickly as they could raise it on television ads and direct mail. In the period covered by the new reports, which started about two weeks before the Nov. 6 election, supporters said they raised $735,513, compared to $697,572 by opponents.

Marylanders for Marriage Equality listed small-dollar contributions from hundreds of donors, but the biggest chunk of its money in the closing weeks came from the Human Rights Campaign, the nation’s leading gay-rights lobby.

The HRC gave about $311,000, including direct donations, transfers from a political action committee and in-kind contributions.

Freedom to Marry, another national group, contributed $70,000 shortly before the election.

Less expected was a $75,000 contribution from MGM Resorts, the Las Vegas-based company angling to build a casino at National Harbor in Prince George’s County. MGM prevailed in a far more costly campaign this month to expand casino-style gambling in Maryland.

“MGM Resorts celebrates diversity in all aspects of its business and is a longtime supporter of workplace equality,” the company said in a statement Wednesday in which it said its “modest” donation to Marylanders for Marriage Equality was a sign of continued support for gay-rights issues.

MGM has been recognized by the Human Rights Campaign for its non-discrimination and benefits practices affecting gay employees.

The Law Offices of Peter Angelos also kicked in $50,000 to the same-sex marriage campaign days before the election. Angelos, a prolific Democratic donor, is owner of the Baltimore Orioles.

The Maryland Democratic State Central Committee gave $10,000, and leading Democratic supporters of the ballot measure also chipped in money for the marriage measure from their campaign committees.

Those included House Majority Leader Kumar P. Barve (D-Montgomery), Del. Benjamin S. Barnes (D-Prince George’s), Del. Guy J. Guzzone (D-Howard) and Del. Justin D. Ross (D-Prince George’s) — all of whom gave $1,000.

The political action committee of Gov. Martin O’Malley (D) gave $1,000 as well, and his chief lobbyist, Joseph C. Bryce, contributed $1,000 in personal funds.

The bulk of the money raised by the Maryland Marriage Alliance in the closing weeks of the campaign came from two national groups opposed to same-sex marriage.

The National Organization for Marriage gave $400,000, bringing its total for the campaign to $1.2 million, and the the Knights of Columbus contributed $100,000, according to the report.

Money also came in from Roman Catholic dioceses from around the country, including $25,000 from Newark, N.J.; $10,000 from Wheeling, W.V.; and $5,000 from Arlington, Va.

Other notable donors included: Sen. C. Anthony Muse (D-Prince George’s), who gave $1,000; William E. Lori, the archbishop of Baltimore, who gave $2,000; and Michael Peroutka of Pasadena, Md., who has run for president as a member of the Constitution Party. Peroutka gave $10,000, according to the report.