Very good question, actually.
Unless Sandoval runs, Masto is probably favored though not safe. Democrats are pretty good at getting their voters out in midterms here (2014 was an exception for obvious reasons), so I'm not sure a good year for Republicans would be enough to flip this seat. I don't see it flipping before AZ, and it definitely doesn't flip before NH.
Lean D. Nevada Republicans don't have much of a bench, and the Reid machine seems to turn out Democrats in Clark County even in most midterm elections. If CCM runs a strong campaign, she should win narrowly.
Cortez Masto is safe against anyone whose name isn't Brian Sandoval.
Laxalt would be one of the weaker opponents for CCM. He's a proven loser, running retreads statewide typically doesn't work. He definitely could win, but CCM would be the favorite unless 2022 is a massive wave.
Laxalt would be an incredible gift to Masto.
Of the Dems three vulnerable seats (NH, NV, and AZ), I would say this is the one with the best chance to stay D. The Reid machine will be in full force trying to re-elect CCM and Sisolak and I actually think that Nevada may actually now be the mirror image of Florida. A very inelastic state where Republicans can get very close statewide, but have a very hard time actually winning.
I guess the closest analogue for this race might be 2010? Obviously Reid was the Majority Leader at the time, and Angle wasn't exactly a good candidate, but the Democrats in Nevada have proven that they can win races in unfavorable years numerous times in the past.