Despite landslide victories on Tuesday, Donald Trump still needs to win Indiana — and he's starting to act like it.

The frugal Manhattan mogul has begun opening his wallet for the air war, spending more than $900,000 on TV and radio ads. He's working the inside game, wooing Gov. Mike Pence one-on-one in what multiple Indiana insiders said appears to have been a successful effort to keep the governor on the endorsement sidelines. And Trump's new campaign strategist Paul Manafort has been telling Republican officials, multiple people told POLITICO, that Trump is in the midst of doubling the ground team there, with plans to balloon his in-state operation to 40 people.

The sudden infusion of operatives, cash and attention is a sign of Indiana's fulcrum position in the Republican primary fight. Trump can't win the nomination there. But it's where he could lose it.

A 40-person state operation would be one of Trump's most notable investments in a field program of the cycle. And Manafort clearly has an interest in proving to GOP insiders that his candidate is willing to fund a more robust campaign operation, both to lock up the nomination and to demonstrate that he's ready to do what it takes to win a general election expected to cost each side more than $1 billion. But sources close to the campaign cast doubt on Manafort's closed-door claims about Indiana, asserting he was exaggerating both the current head count and the planned one.

"We're doing the same things we've done in the other states," said one Trump operative. Those sources questioned whether the last-minute ramp up would have an impact before the May 3 primary. "Typical political embellishment," said a second campaign source of Manafort's claims. "I'm not sure we have that many that could get there and actually be productive. It's too short of a timeline."

Indiana is critical. If Trump doesn't carry the state and most of its 57 delegates on May 3, his path to lock up the 1,237 delegates he needs would require a near-sweep of California — a tall task with 53 independent congressional district elections — or picking off another state or two where he's currently not favored, such as South Dakota or Montana.