According to the FEC filings, Clinton's campaign committee has spent $564 million this campaign, vastly more than the $321 million Donald Trump's campaign committee spent. After including the amount raised by super PACs and other party and jointfundraising committees, the divide in spending gets even wider. The Washington Post estimates that more than $1 billion had been raised to support Clinton, versus $795 million to support Trump. Funds raised by Clinton-backers in outside groups totaled $189 million, while Trump PACs and super PACs raised only $59 million. (See also, What Happens to Campaign Contributions After Elections?)
For those looking for answers about what happened this election, the details of campaign donations may offer some clues.
Donald Trump has been credited with claiming the votes of millions of Americans who have no place in the establishment and running a populist campaign. He promised to change the status quo and accused Hillary Clinton of rigging the economy with the global power structure against the working class. Trump contributed $56 million of his own money to the campaign and spoke of his independence from special interests. According to the Center for Responsive Politics, small individual contributions (less than $200) accounted for 27% of the donations towards his campaign and large individual contributions (more than $200) accounted for 15%. Compare this with Clinton's campaign which received 18% in small individual contributions and a whopping 53% in large individual contributions.
The candidate to have a higher proportion of small individual contributions than both these candidates was Bernie Sanders with 59%. There is a reason he reiterated that the average donation he received was $27. Smaller contributions implies grassroot support, whereas the support of large donors, while helpful, is looked at suspiciously by most. It also looks like it amounts to very little if the votes and support from regular Americans don't exist. Not many believed Trump when he spoke of the "silent majority" but it looks like it existed all along, sending him small donations and waiting for their chance to cast their ballot.