(CNN) Vermont Sen. Bernie Sanders seems to be the third wheel among the Democratic frontrunners. Former Vice President Joe Biden has held a consistent advantage in national primary polls. Massachusetts Sen. Elizabeth Warren seems to have the crowds and momentum .

Meanwhile, Sanders is often treated as 2016 leftovers.

I'm not sure what chance Sanders has of winning the nomination, but the national and early state polling suggest Sanders shouldn't be tossed aside as an afterthought. He remains a key player in this Democratic race.

Sanders is at 15% nationally in an average of debate qualifying polls over the last month. That may not seem like a lot, but it's actually very close to Warren's 18% average. Sanders actually runs slightly ahead of Warren in a number of polls, including one released by ABC News/Washington Post this past weekend, in which Sanders was at 19% and Warren was at 18%.

Importantly, Sanders isn't dropping. His 15% in national polls is what he's averaged basically all year with the exception of a post-announcement bump in March. Sanders is not like California Sen. Kamala Harris, who started in the single digits, rose after she announced, dropped, rose again after the first debate and then dropped a second time. Having 15% support is key because it means he's at the threshold to receive delegates in primary contests

The early state picture is a little more cloudy, but it may actually be better for Sanders. CBS News/YouGov polls released this past weekend have him in first place or within 3 points of first place in Iowa, New Hampshire and Nevada. I should point out that earlier polling suggests he may be in a worse position in Iowa and Nevada than YouGov found. There is little question, though, he's in the hunt in New Hampshire , the neighboring state of his home, Vermont. Almost all of the polling has him within the margin of error of first place. Even in Iowa and Nevada, the average of public polls have him tied and ahead of Warren, respectively.

There's also reason to believe that Sanders' base is firmer than it is for other Democrats. A recent Pew Research Center poll found that only 47% of his supporters are excited about candidates besides Sanders. A majority of the supporters for all the other Democrats in the top four (Biden, Harris and Warren) were excited about other candidates. The vast majority of Warren backers (80%) were excited about several candidates.

Furthermore, Sanders' backers like him for issue stances. In a year in which electability is taking precedence over issue agreement for many voters, Sanders is the only top tier candidate who does better among those who say issue agreement is more important to them than electability. That's important because you can easily imagine someone changing their mind on who is most electable. It's harder to imagine them switching if they are with a candidate because of the issues.

Of course, merely having a good base doesn't mean it's easy to expand upon it. Sanders has near universal name recognition among voters, and he's at 15% nationally. Additionally, he's gained relatively little support from fellow elected officials, which usually correlates with failure in the primary.

Still, in a 20-person primary in which most candidates can't get above 2%, Sanders has consistently done so. Even if he doesn't win, he's got far more influence than most running.