It took a year, but Hillary Clinton finally seems to be building momentum as the Democratic nominee for president. That includes a gusher of money starting to flow her way.

Victories in the final week of state primary elections finally gave Clinton enough delegates to make her the de facto Democratic nominee, facing off against Republican counterpart Donald Trump. And almost immediately, Clinton won one of the most coveted endorsements in politics: Billionaire hedge-fund manager Tom Steyer, the most prolific Democratic donor of recent times.

Steyer donated $73 million to candidates in the 2014 midterms, most of it through his own super PAC, NextGen Climate Action. For the 2016 cycle, he's donated $13 million so far. Steyer is a devout environmentalist who mostly spends his money campaigning against Republicans who dispute the effects of climate change and the need for solutions. Steyer didn’t say how much he’d be willing to spend on Clinton, but his endorsement suggests he may contribute more than if he were merely supporting the Democratic cause generally.

Clinton already has a sizable funding advantage over Trump. Between her campaign and various super PACs supporting her, Clinton had more than $80 million on hand at the end of April. Trump had just a couple million. Trump has self-financed about 75% of his campaign up till now, but even billionaire Trump has nowhere near the liquid assets to fund a battle with a candidate who could easily raise $1 billion, when super PACs and other sources are combined.

Republican finance guru Fred Malek said recently that Trump could face a fundraising shortfall of $300 million to $500 million. That would be a giant gap, especially considering that Republican Mitt Romney lost to Democrat Barack Obama in 2012, even though fundraising was roughly even between the two candidates.

There’s no lack of wealthy GOP donors. But they don’t automatically write million-dollar checks just because a candidate shows up. And Trump spent most of the campaign so far bashing super PACs and by extension their donors, portraying the whole arrangement as part of the rigged system Americans are sick of. Trump is now assembling a traditional fundraising team, but he’s years behind Clinton, who started raising money for her presidential bid in 2014 – and has a network to call on that dates back more than 20 years, to her husband’s presidency.

Trump will probably snag some big donors – including possibly Sheldon Adelson, the casino baron who spent roughly $100 million on GOP candidates in 2012, making him the single biggest donor in that cycle. But wealthy GOP donors have already blown $400 million on failed candidates such as Jeb Bush, Marco Rubio and Ted Cruz. Some are fed up with their party’s presidential prospects and focusing on Congressional races or state-level contests. In this contest, Trump the dealmaker may have to settle for less than he feels he deserves.

Rick Newman’s latest book is Liberty for All: A Manifesto for Reclaiming Financial and Political Freedom. Follow him on Twitter: @rickjnewman.