The money just couldn't stop him. Donald Trump will likely become the Republican presidential nominee after a decisive victory in the Indiana primary and the departure of Texas Sen. Ted Cruz on Tuesday night. Tweet

That milestone comes after groups opposing Trump's candidacy spent heavily to prevent his coronation. But where was the return on investment?

Outside organizations, which can support or oppose a presidential hopeful without coordinating with a candidate or party, have spent $43.3 million against Trump, according to the Center for Responsive Politics. That compares with $13.3 million in spending by outside groups supporting Trump.





Protesters outside the hotel where Donald Trump was speaking, Burlingame, California, April 29, 2016. Josh Edelson | AFP | Getty Images

Those organizations, as well as Trump's GOP rivals, had funneled resources into knocking down the bombastic businessman as he pulled in more pledged delegates toward the party's nomination. Cruz and Ohio Gov. John Kasich, who sources say plans to suspend his campaign Wednesday night, had attempted to unify the non-Trump vote. But in Indiana, which Cruz and many political observers had called a critical juncture in preventing a Trump nomination, their efforts came up short. Trump garnered more than 50 percent of the vote, easily handling Cruz.

With Cruz dropping out, Trump took a remarkably cheap path to becoming the party's likely nominee.



His campaign committee spent $46.3 million through the end of March, according to the Center for Responsive Politics. The bulk of its funding, roughly $36 million, came in loans from Trump himself, while $12 million was contributed. Cruz's campaign committee spent nearly $70 million through the end of March, while outside groups supporting him chipped in more than $42 million.

On the Democratic side, campaign committees for former Secretary of State Hillary Clinton and Vermont Sen. Bernie Sanders have each spent more than $150 million. Outside groups have used more than $30 million supporting Clinton.

Only Kasich has spent less than Trump among the candidates still in the race entering Tuesday.