After the 4th wave of entrance polls from Nevada (sample of 1024 caucusgoers), Sanders leads 53-45 with Latino voters. Hispanics make up 19% of caucusgoers, up from 15% in 2008.
Even if that doesn’t hold and it ends up being closer to a tie (or even if Clinton only narrowly wins) among Latinos/Hispanics, that punches an enormous hole in the Clinton campaign's alleged “non-white” firewall.
Among non-whites overall, Clinton leads only by a 56-42 margin. That is because she won African Americans 76%-22%. Sanders leads among whites by 49-47.
In reality, Clinton’s firewall is more narrowly limited to African Americans — who are backing her strongly, though not quite as strongly as they backed Obama in 2008. African American vote share is down to 13% from 15% in 2008, without Obama on the ballot. That is also is bad news for Clinton, given that African Americans are her best demographic in polls so far.
Sanders also did very well among Hispanics in Iowa. He won most of the most heavily Hispanic precincts in Iowa. He also roughly tied Clinton in the most heavily non-white precincts in Iowa:
Statistical estimates of vote by race in these precincts find that Hispanics may have backed Sanders by as much as 2 to 1 in these precincts:
Hispanics backed Clinton big in the 2008 primaries, usually by 2 to 1 margins over Obama. So far, it doesn't look like that is going to be the case in 2016 at all.
So when western states like Colorado, Arizona, and New Mexico eventually vote, Sanders should do very well. And if Clinton doesn't win Hispanics, Sanders could do better than expected in Texas, even though Clinton remains favored there.
And then at the end of the primary period, there’s the big one - California.
With support from Hispanic voters, Bernie Sanders can win California and he can win the Democratic nomination.
Update — I found precinct results, and from those it looks to me like Sanders probably didn’t actually win Hispanics outright. My best guess now is that Clinton probably won among Hispanics, but by a relatively small margin. In Las Vegas it looks like Clinton won most of the most heavily Hispanic precincts, though Sanders did win some of them. Eyeballing it, it appears that Sanders may have done a bit better among Hispanics in Reno than in Las Vegas — it looks like he won as many if not more of those precincts than Clinton. But Reno has a smaller population.