The Ted Cruz-John Kasich alliance failed on Tuesday night as Donald Trump rolled up huge victories in five Northeastern states. The two anti-Trump candidates have only one real option left: to double down on the troubled strategy.

With Kasich out of the way in Indiana next week, Cruz faces a must-win showdown against Trump. If the billionaire takes that state, it may be close to impossible to stop him from winning the Republican presidential nomination. If Cruz prevails, however, his camp and Kasich’s already are discussing a plan for dividing up the final huge primaries on June 7.

Trump’s pathway to the 1,237 delegates necessary to capture the nomination became easier with big victories on Tuesday. He won more than 100 delegates, putting him less than 300 shy of the magic number.

On the Democratic side, Hillary Clinton continued her seemingly inevitable march to the nomination, winning four of five contests: Pennsylvania, Maryland, Delaware and Connecticut. But Sen. Bernie Sanders, her only rival, won Rhode Island and insists that he will keep competing at least through the final June primaries.

In Indiana, the focus will be on the contest between Trump and Cruz. Fifty-seven delegates are at stake, about half of them awarded winner-take-all on the basis of the statewide vote. The remainder are awarded winner-take-all in each of the nine congressional districts. Kasich has agreed not to formally compete in the Hoosier state and Cruz, in turn, will stay out of New Mexico and Oregon primaries, which occur later.

Trump dominates the mathematics of the delegate chase and the momentum, too. He is leading in Indiana polls.

His march to the nomination would be slowed if Cruz beat him in that state. Even then, however, Trump would have a big advantage.

In response, the Cruz and Kasich campaigns already are discussing the possibility of extending their pact to the June 7 primaries, when 303 delegates are at stake, including 172 in California.

But such a deal is contingent on how well Indiana works out. The uneasy cooperation, forged at Republican National Committee meetings last week, is already fraying — Kasich seems uncomfortable — and has caused some backlash.

A possible arrangement for June 7 might look something like this: Cruz would focus on California and most of the congressional districts; Kasich might limit his presence to 10 or 12 districts, chiefly in northern California.

But the Ohio governor could try to take on Trump in New Jersey, a winner-take-all state. Trump is backed by Governor Chris Christie and has proven unbeatable in other Northeastern states.

Yet Christie is unpopular in his home state and Kasich has a more impressive record as a governor. The case for Kasich might be strengthened by Trump’s poor poll ratings in general election match-ups, nationally and in key states. For example, though he won the Pennsylvania primary handily, general election match-ups show Clinton running well ahead of him in the the state.

That’s hardly comforting for anti-Trump Republicans, who face a steep uphill slog, but it’s all they have.

(c) 2016, Bloomberg View · Albert Hunt