The symbolism was too powerful to ignore. As anyone who watched Israeli Prime Minister Benjamin Netanyahu’s speech last week in Congress knows, one of the people prominently seated in the House gallery was the casino magnate Sheldon Adelson, a primary financial backer of both the Republican Party and Netanyahu. As The Washington Post’s Colby Itkowitz reported, at one point Adelson’s wife, Miriam, accidentally knocked her purse off the House gallery railing and it hit Representative Brad Ashford, a Nebraska Democrat seated below. The Post noted that Adelson had given $5 million to the G.O.P.’s Congressional Leadership Fund super PAC, which had spent $35,000 in a failed effort to defeat Ashford in his 2014 race against Representative Lee Terry. Ashford later joked to The Omaha World-Herald: “I wish I’d opened the purse. Do you think she carries cash?”

We certainly know that Mr. Adelson does. And when it came to showering that cash on Republican presidential hopefuls and right-wing PACs trying to defeat President Obama (reportedly $150 million in 2012), and on keeping Netanyahu and his Likud party in office, no single billionaire-donor is more influential than Sheldon. No matter what his agenda, it is troubling that one man, with a willingness and ability to give away giant sums, can now tilt Israeli and American politics his way at the same time.

Israel has much stricter laws on individuals donating to political campaigns, so Adelson got around that in 2007 by founding a free, giveaway newspaper in Israel — Israel Hayom — whose sole purpose is to back Netanyahu, attack his enemies in politics and the media, and enforce a far-right political agenda to prevent any Israeli territorial compromise on the West Bank (which, in time, could undermine Israel as a Jewish democracy). Graphically attractive, Israel Hayom is now the biggest-circulation daily in Israel. Precisely because it is free, it is putting a heavy strain on competitors, like Yediot and Haaretz, which both charge and are not pro-Netanyahu.

Adelson then bought the most important newspaper of the religious-nationalist right in Israel, Makor Rishon, long considered the main backer of Netanyahu’s biggest right-wing rival, Economy Minister Naftali Bennett. Last March, in an interview with Israel Army Radio after the Makor Rishon sale, Bennett said: “It saddens me. Israel Hayom is not a newspaper. It is Pravda. It’s the mouthpiece of one person, the prime minister. At every junction point, every point of friction between the national interest and the interest of the prime minister, they chose the side of the prime minister.”