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Wisconsin Gov. Scott Walker just returned from one of the rites of passage for presidential hopefuls, a pilgrimage to Israel. He followed a well-worn path that will be trod several times by his rivals who believe the road to the White House goes through Jerusalem.

Ostensibly Walker, a Republican, and the others are honing their foreign policy credentials, but that’s not the real reason. The real goal is to win the pro-Israel primary by impressing deep-pocketed Jewish donors like casino mogul Sheldon Adelson. That’s why Walker quickly tweeted his picture shaking hands with Prime Minister Benjamin Netanyahu and another taken at the Western Wall. The unstated inscription on the pictures was, “Dear Sheldon, Hey, look at me here with your boy Bibi.”

Walker’s trip was financed by his own PAC and by the Adelson-funded Republican Jewish Coalition, which has been running such trips for years. Texas Gov. George W. Bush took that trip in 1998, when he got a helicopter tour from Ariel Sharon; Walker also got a chopper tour, with a nephew of Moshe Dayan. Sen. Barack Obama went in 2008 after securing his party’s nomination.

The Republican presidential contender pilgrimages have been going on for months and will continue into next year. Sen. Marco Rubio is expected in Israel this summer. No candidate in either party has been to Israel as often as Mike Huckabee. Other recent visitors include Sens. Rand Paul, Ted Cruz and Lindsey Graham as well as Ben Carson, Bobby Jindal, Rick Perry, Chris Christie and Rick Santorum.

On the Democratic side, Hillary Clinton has made numerous trips as first lady, senator and secretary of state. Vermont Sen. Bernie Sanders, the only Jewish candidate, spent several months on a kibbutz following college graduation. Martin O’Malley, who plans to announce his candidacy May 30, has been to Israel several times, most notably as governor of Maryland leading trade delegations.

These trips are often made with wealthy supporters or groups like the RJC. Souvenirs include photos for campaign literature, anecdotes for speeches, some names to drop and a patina of experience.

But it’s mostly about the money — especially on the GOP side, where conservative pro-Israel mega-givers are increasingly important to candidates.

Adelson is by far the biggest and best known among wealthy Jewish donors, but there are a number of others in both parties. He boasted of spending in the neighborhood of $100 million in the last election cycle, mostly to defeat Obama, and indicated he’ll do more this time. The RJC, one of his top causes, claims to have raised $13 million in the 2012 cycle, with at least $4.5 million going for anti-Obama attacks; it plans to spend more in 2016.

The annual RJC meeting at his Las Vegas casino (this year’s was held in April) has been dubbed the Adelson Primary, as a continuous procession of GOP hopefuls audition for the billionaire and a chance to kiss his ring or some other part of the anatomy as visions of his checkbook dance in their heads.

When New Jersey Gov. Chris Christie had the temerity to refer to the West Bank as “occupied territory” in Adelson’s presence, a near mortal sin to the far right, he was quickly informed of his transgression and rushed to beg for mercy.

Rubio tried to amend a Senate bill on Iran nuclear negotiations barring any deal unless Tehran recognized Israel. It was opposed by GOP leadership and the White House, but it had been proposed by Netanyahu, another recipient of Adelson’s generosity. Rubio knew his amendment was a poison pill and would fail, one GOP insider told the National Journal, but it didn’t matter because “he’s working harder to get Sheldon than to solve problems.”

It would also appeal to Rubio’s own Jewish billionaire benefactor, Florida car dealer Norman Braman.

AIPAC and other pro-Israel groups assign “rabbis” to help guide candidates navigate Jewish politics and hook up with political action committees and other donors.

Since Citizens United, wealthy individuals can give unlimited amounts directly to campaigns or through other groups, openly or secretly. Adelson may be the most prominent but other top Jewish Republicans include hedge fund executives Paul Singer and Seth Klarman, home builder Larry Mizel, real estate developers Mel Sembler and David Flaum. and Bay Area software execs Larry Ellison and Safra Catz.

On the Democratic side of the ledger are George Soros, Wall Streeters Marc Lasry and Steve Rattner, L.A. Reid and Haim Saban from the entertainment industry, and Dallas lawyer Marc Stanley. Many are bundlers, people who organize and collect checks from other donors to maximize their impact. Bundlers generally don’t have to be identified

In the wake of the Citizens United and other Supreme Court decisions, a veil of secrecy has replaced the disclosure that was supposed to follow the Watergate scandals.

“The biggest donors in both parties no longer need to endure public scrutiny if they prefer not to. Knowing how much a donor gives, and where, can lead to unwanted publicity and will certainly lead to more fundraising calls. Major donors can largely control what the public knows and what remains secret,” said Aaron Keyak, a Democratic political consultant with Bay Area roots.

Israel plays a larger role in Republican fundraisers because it is seen as their only real appeal to Jewish voters, who remain staunchly progressive in domestic politics.

The great risk is the increasing polarization of support for Israel, particularly under Netanyahu’s influence and his proclivity for meddling in American partisan politics. His 2012 endorsement of Mitt Romney and this year’s congressional speech attacking Obama’s Iran negotiations left a bitter taste among many, especially Democrats.

The new, virtually unregulated environment for campaign giving will add to the importance of pro-Israel big givers, and inevitably widen the partisan gap on the Israel issue.

Douglas M. Bloomfield is the president of Bloomfield Associates Inc., a Washington, D.C., lobbying and consulting firm. He spent nine years as the legislative director and chief lobbyist for AIPAC.