NV-PPP for Democratic PAC: Masto (D) leads Heck (R) by 1.

[Xing]

Democrats always seem to under-poll in Nevada, so if the polls say "tied race" it probably won't be. 

It was the same discourse of the 2014 Colorado Senate race.
http://www.realclearpolitics.com/epolls/2014/senate/co/colorado_senate_gardner_vs_udall-3845.html

(Gardner actually won by 1.9, not 2.5) True, there was no Republican bias in polling of the 2014 Colorado Senate race, but that was in a year when most polls had a noticeable Democratic bias. The Republican bias in Colorado and Nevada polling in 2010 and 2012 was larger than in most states. So, while it isn't a safe assumption that polling in 2016 in these states will have a Republican bias, it's not an unfounded assumption.