The Nevada caucus 2016 has arrived, and while final polls leave an unclear picture as to whether Hillary Clinton or Bernie Sanders holds the advantage, political experts say the momentum in the race belongs solely to Sanders.

There have only been a handful of polls from Nevada in the past few months, as opposed to New Hampshire and Iowa, where there were seemingly one a day in the lead-up to votes there. The polling that did come out this week, from CNN/ORC, showed a very tight race, with Clinton taking 48 percent support and Sanders with 47 percent.

But the Nevada caucus polls themselves may not give much. Political experts and local leaders note that polling in the state has traditionally been difficult, and with only three Democratic polls, there is an incomplete picture of which way voters are moving.

This is true for both the Democratic and Republican votes.

“It’s a total mystery what’s going to happen,” Lt. Gov. Mark Hutchison, a Rubio supporter, told Yahoo News. “The people who do this for a living are saying, ‘Who knows?’ “

Andrew Romano of Yahoo News noted that before the last Democratic caucus in the state back in 2008, the final polls vastly underestimated Hillary Clinton’s strength.

“The same thing happened on the Democratic side. In the final average, Hillary Clinton was four percentage points ahead of Barack Obama: 37.8 percent to 33.8 percent. John Edwards trailed with 18 percent. The actual caucus results, however, were wildly different: 50.7 percent for Clinton, 45.2 percent for Obama, 3.8 percent for Edwards.”

Part of that is the relatively new nature of caucuses in Nevada, Romano noted, with the first being held in 2008. This makes is much more difficult for pollsters to identify likely caucus-goers.

But there is already evidence that Bernie Sanders has cut into her national lead, and he has done so dramatically. Clinton held a 52-point lead just one year ago, with 55 percent support to Sanders’ 3 percent, but a new poll released Thursday by Fox News showed Sanders in the lead for the first time this race, with 47 percent support to her 44 percent.

“One thing that is clear from our poll — and others — is that Clinton has been losing support and Sanders has been gaining,” Democratic pollster Chris Anderson told Fox News. “And this process appears to have accelerated since the contests in Iowa and New Hampshire.”

Politico's @anniekarni captures what's happening on the ground here on the eve of the Democratic caucus. Must-read:https://t.co/PO6QcfLi4p — Jon Ralston (@RalstonReports) February 19, 2016

Republican pollster Daron Shaw added that Sanders may have seized momentum after a win in New Hampshire and a very close loss in Iowa.

“Historically, lesser-known candidates beating establishment candidates in early contests have seen the biggest boost in their national support,” Shaw said.

"It’s clear to me both campaigns agree that Sanders has momentum." -@chucktodd talks Nevada caucus. https://t.co/dTlZhWfQ60 — TODAY (@TODAYshow) February 19, 2016

Bernie Sanders could also be gaining an “electability” boost, with a number of national polls showing him as a stronger general election choice than Hillary Clinton. Real Clear Politics shows that in a hypothetical matchup, Sanders leads Donald Trump by a 10-point margin, 50 to 40 percent. Hillary Clinton leads by only a 5-point margin, close to the margin of error for polls.

Nate Silver of FiveThirtyEight noted that even with these factors, Hillary Clinton is still favored to win the 2016 Nevada caucus, but he also admitted that the picture is unclear.

“Nevada has a fairly high nonwhite population, but it isn’t especially liberal. Clinton was also well ahead of Sanders in the (relatively small sample) of interviews Morning Consult conducted there earlier this year. It’s possible that Clinton will be hurt because the state holds a caucus, although we don’t have a lot of evidence yet about which Democrat that benefits. In other words — and as much as her campaign might try to avoid admitting it — it’s a state that Clinton “should” win. Conversely, a Sanders win would be a sign he has staying power.”

There could be a factor more important that final polls in the 2016 Nevada caucus. With not much background on caucusing in the state, the campaign that carries a better ground game and does a better job bringing their voters to the caucuses will have a big advantage. That will likely be the biggest test for Bernie Sanders.

[Photo by Bill Pugliano/Getty Images]