The Texas senator — more than ever before — is the most viable alternative to Donald Trump based on the delegate count. But he is still striving to move major donors off the anti-Trump sidelines and into the pro-Cruz fold, even after his big Wisconsin win Tuesday.

But this weekend, Cruz and his allies will make their most aggressive play yet to rally top GOP megadonors. The center of activity will be at Sheldon Adelson's Venetian hotel and casino in Las Vegas, where Cruz will meet both his own top bundlers and super PAC patrons as well as deliver a speech to the Republican Jewish Coalition.

Given that Cruz has been on the trail non-stop, it's essentially a chance for the donors to meet the man they can help push over the top.

Donors have given Cruz a lot of consideration, said one person involved in Cruz's big-money operation, "but no one's jumped yet."

The timing is critical. Cruz is hardly in dire straits financially -- he raised $2 million on Tuesday, his campaign said, and his super PACs sit on a largely untouched financial reserve of tens of millions of dollars. But the race is about to get much more expensive, as candidates will need more cash than ever before to advertise in a battery of states that would stress even a well-funded campaign's coffers, beginning with New York on April 19, followed closely by Pennsylvania and then California in early June.

Las Vegas Sands Corp. Chairman and CEO Sheldon Adelson speaks at the Global Gaming Expo (G2E) 2014 at the Venetian Las Vegas on October 1, 2014 in Las Vegas, Nevada.

Adelson has long been an elusive target. The casino magnate poured millions of dollars into the 2012 race, but has yet to substantially back any candidate this year. He did give the Cruz campaign the maximum personal donation of $2,700 last year, but has not yet signaled that he will substantially invest in Cruz's bid despite the exit of Marco Rubio, his perceived favorite, from the race weeks ago. Top Republicans will converge on Vegas on Thursday evening for dinner at Adelson's home.

The Cruz campaign declined to comment for this story.

Cruz will address the RJC winter meeting on Saturday afternoon -- the only remaining presidential candidate to make the trip to Las Vegas.

The Jewish group has long been friendly terrain for Cruz, who is seen by them as a strong advocate for Israel's security and who won plaudits for his appearances before the group both last year at the Venetian and this winter in Washington. Yet the group has an establishment bent, and several of its leaders were firmly ensconced in the fundraising worlds of Rubio or Jeb Bush.

Now, they're up for grabs. While Trump's professed desire to be "neutral" between the Israelis and Palestinians in order to cut a deal stoked significant discomfort, he largely neutralized concerns with a well-received, prepared speech at an AIPAC conference last month, Jewish leaders say.

"They're just as flummoxed and just as mystified and just as up in the air about this race as anyone else," said Shmuley Boteach, a rabbi close to Adelson and several other prominent Jewish donors. "I personally have not heard a consensus that it should be Cruz or Trump."

Even Adelson, when reportedly asked in February about supporting Trump, could only offer a, "Why not?"

Cruz's emissaries to the RJC world — led by board member Ed Czukar and million-dollar Cruz donor and longtime friend Adam Ross — are expected to court their associates hard at the Vegas conclaves. And even if they may no longer find Trump's language on Israel objectionable, some believe the Republican Jewish world will be convinced that Cruz does not threaten the pro-Israel GOP majority in the Senate as Trump might.

Cruz backers expect many of these leading RJC donors to drop by the conveniently timed Cruz super PAC summit. The group will host dinners and receptions for donors on Friday and Saturday at The Venetian, according to attendees. The super PAC rents out separate rooms and hosts separate briefings to comply with election laws, but Cruz himself and his wife, Heidi, are expected to visit.

Las Vegas is also a test for that revamped operation. The unique super PAC structure -- a half dozen smaller groups controlled by different big donors and operatives -- has long been flush with cash, but confused top donors and did not give them a clear place to park their dollars. Super PAC officials believe that their new Trusted Leadership organization, a traditional model under a single umbrella, now makes it easier for big givers to actually give big.

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So far, they haven't. Many of the party's traditional serious political donors -- especially those previously cutting checks for other candidates — have not rushed to Cruz's shop. While Cruz can count megadonors like Bob Mercer and Richard Uihlein as backers, the other top financiers in 2012 and 2014 have instead chosen to invest their money in efforts to tear down Trump rather than build up Cruz.

Neither of the top two disclosed backers of groups dedicated to stopping Trump — the Stephens family of Arkansas and the Ricketts family of the Midwest -- has donated substantial money to Cruz or his super PACs, according to campaign finance records.

These anti-Trump donors are still boosting Cruz indirectly, especially in contests like Wisconsin where multiple super PACs savaged the billionaire with negative ads. And that win likely paves a smoother path this weekend when Cruz and his allies pass the hat to expand their financial base.

Cruz donors are subscribing to the adage that winning begets winning. Boyden Gray, a longtime Washington lobbyist who backed Bush but recently signed onto Cruz's finance team, said more and more contributors are transforming from Trump foes to Cruz friends.

"I see a movement of that kind taking place," Gray said. "Does it cover everybody who's trying to stop Trump? No, I don't know."