Sen. Ted Cruz faces a critical test in Indiana’s Republican primary May 3. While a loss would not eliminate him, it would make his efforts to stop Donald Trump even more challenging. (Michael Conroy/AP)

After his clean sweep of five primaries Tuesday, the options for denying Donald Trump the Republican presidential nomination continue to dwindle rapidly — so swiftly, in fact, that next week’s primary in Indiana now appears to be a make-or-break event for the stop-Trump forces and especially the candidate running second, Sen. Ted Cruz (Tex.).

What happened in Tuesday’s primaries was not wholly unexpected. Trump was playing on home turf, in states where Republican voters for the most part are less ideologically conservative than in other areas of the country. But as with his victory in New York a week ago, just because something was predicted doesn’t mean it isn’t significant.

Which is why the losers — Cruz and Ohio Gov. John Kasich, who are now in an odd-couple alliance to stop Trump — did what losing candidates have done throughout this long primary season. They tried to make the best case they could that the battles ahead, not those just concluded, are the ones that really count. They are left to cling to no more than that.

For Trump’s rivals, all is now a numbers game — including the challenge of making everyone believe that the front-runner can be kept short of the 1,237 delegates needed to win on the first ballot at the convention. Based on raw arithmetic, it’s not unreasonable for Cruz, Kasich and others in the party who don’t want Trump as their nominee to express hope-to-confidence that he can be stopped.

Under the many possible projected outcomes in the remaining 10 states, Trump will either end up just over that magic number or somewhat short of it. At some point after June 7, the last day of GOP primaries, it will be known whether Trump has a hard list of delegates who will vote for him on the first ballot — those who are bound to him on the basis of primary and caucus results, or those who are not bound but have made public pledges to him.

Republican presidential candidate Ted Cruz held a campaign rally in Knightstown, Ind., on Tuesday after the primary races in Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island. (Reuters)

But there is more at work than just counting numbers. When Trump broke the 60 percent barrier in the popular vote in New York, it forced many Republicans to take notice and begin to acknowledge, if grudgingly, that he seemed more likely than before to prevail. That feeling could gather force on the basis of his powerful showing Tuesday night, when in state after state he rolled up huge margins.

Beyond his victories, there was evidence in the exit polls to suggest that the will among rank-and-file Republicans to stop a Trump nomination, even if he falls a bit short of 1,237 at the end of the primary race, might not be as strong as Cruz, Kasich and the GOP establishment would like to see.

Those exit polls indicated that majorities of Republicans who voted Tuesday say the candidate who has won the most — insert here your choice of states, delegates or raw votes — should end up becoming the nominee. Beyond that, there was evidence that in these states, at least — and granted, the five states composing Tuesday’s battlefield hardly constitute Cruz country — more voters said they couldn’t vote for the Texan in November than said that of Trump.

Republican National Committee Chairman Reince Priebus has said repeatedly that coming close won’t determine the nomination, that the nominee must break the 1,237 barrier. That’s a message some of the leaders in the stop-Trump movement are trying to reinforce, no matter what has happened on the past two primary nights.

Katie Packer, who oversees the anti-Trump super PAC called Our Principles, said nothing that has happened this week or last changes her group’s calculations about blocking Trump.

“What we’re communicating to people,” she said, “is the same we communicated to people before New York and after New York, that the last primary day [April 19] and this primary day were not going to be particularly good days. . . . We always planned to move beyond these two dates.”

Packer sees California as the ultimate arbiter of the success of the stop-Trump forces, if only because the state will award 172 delegates on June 7. But as a practical matter, Indiana and the 57 delegates up for grabs in its winner-take-all contest next Tuesday loom even larger. A Trump victory next week would amplify calls for the party to begin to rally behind him.

Cruz knows this, and that explains the unusual pact between the senator from Texas and the Ohio governor, which the rival campaigns announced late Sunday and which Trump attacked mercilessly Monday — and which has been in a fragile state ever since Kasich went off the reservation in describing it Monday.

Kasich, whose only strategy is to have the GOP nomination contest go beyond two or three ballots in Cleveland, has agreed to throttle back his campaign efforts in Indiana (though he was in the state Tuesday raising money). That will give Cruz what he long has wanted: a clean matchup against Trump. In return, Cruz will not invest in later primaries in New Mexico and Oregon.

Cruz has had success in corralling delegates in inside combat at recent state conventions, outmaneuvering Trump to the point of embarrassment. But those delegates aren’t all available to him on a first ballot. Some will go to Cleveland bound to Trump. Cruz needs to deny Trump those 57 Indiana delegates or face the reality that his candidacy could come to a bleak conclusion.

Had Cruz met some of his earlier targets in this race, he might not be looking at a do-or-die face-off in Indiana. By his own game plan, he was supposed to win South Carolina in February. Instead, Trump romped and won every delegate. Cruz was supposed to have a big day March 1, when many Southern states cast ballots. He won Texas and Oklahoma, but Trump won Alabama, Arkansas, Georgia and Tennessee.

Trump has shattered Cruz’s goal of consolidating conservatives. Cruz was planning to nail down the evangelical vote, but Trump has won evangelicals in at least twice as many states as Cruz. Before Tuesday, among GOP voters who do not have college degrees, Trump had won in 18 states to Cruz’s four. In the contest for the most conservative voters, Cruz had won them in more states than Trump, but only by a handful. Trump had won those who call themselves “somewhat conservative” in 18 states to Cruz’s three. Those patterns continued Tuesday.

GOP strategist Russ Schriefer, who was an adviser to the campaign of New Jersey Gov. Chris Christie, said the uncertainty about the outcome remains real. “Cruz is playing the hand that he has been dealt as well as he can play it,” he said, pointing to the candidate’s efforts to raise doubts about whether Trump can get to 1,237, his announcement that he is vetting a shortlist of candidates to be his running mate and his sketching out of scenarios under which he could claim the nomination. “Whether it’s real or not, optically it’s smart,” Schriefer said.

Republican pollster Neil Newhouse, who was an adviser to the super PAC supporting former Florida governor Jeb Bush’s campaign, called these efforts a late-game, Hail Mary play. “They’re not sure any of this is going to work, but they don’t want to leave any stone unturned, any tactic untried,” he said. “I’m sure they’ve got to believe this is incredibly uphill, but the rule of campaigns is you never stop working and fighting and searching for the path to victory.”

Cruz must survive to Cleveland and hope that Trump’s first-ballot strength will be his high-water mark. A defeat in Indiana, though not a mathematical ending to the nomination battle, would nonetheless be a crippling blow to what is left of his strategy for winning.