If you're looking for answers in this world, particularly about politics, you can usually figure out a lot if you follow one simple rule: Follow the money.
Crowdpac recently looked into the zipcodes where Bernie Sanders and Hillary Clinton out-perform each other the most in terms of fundraising and was able to pinpoint where their biggest supporters reside.
It found the most pro-Sanders zip codes in America are in the Mission District in San Francisco, Ithaca, Seattle, Oakland and the Upper West Side in Manhattan.
Correspondingly, Crowdpac found the most pro-Clinton zipcodes are in West Washington, DC, the Upper East Side of Manhattan, Atherton (in the heart of Silicon Valley), Beverly Hills, and Aspen.
Crowdpac's analysis also revealed a stark disparity in terms of the average household incomes of the biggest supporters of the two Democratic candidates.
The average household income of the most pro-Clinton zip codes is $448,000 a year. Comparatively, the average household income of the most pro-Sanders zip codes is significantly less: $103,000 a year.
As Crowdpac highlights, Clinton's campaign has raised $123 million so far in this election cycle (excluding $16 million to her Super PAC Priorities USA), while Sanders has raised $97.4 million from donations averaging $27 (Sanders doesn't have a Super Pac).
The income gap between the staunchest supporters of Clinton and Sanders might also help explain the fundraising gap.
At present, Hillary Clinton has a significant lead over Bernie Sanders in terms of both delegates and the popular vote. But polls show her leading by just 2 points in California ahead of the Democratic primary there on June 7.
Sanders has a very tough road ahead, and it seems very likely Clinton will win the Democratic nomination. But a win for Sanders in California would provide him with both momentum and justification to stay in the race, as many have called for him to drop out in recent weeks.
The Vermont senator recently said he believes he has a "good chance" to win in California. Only time will tell, but we are coming down to the wire in this primary season.