More likely? Tester winning or Cruz losing?

[ClassicElectionEnthusiast]

Between Jon Tester tending to position himself just enough to the right on issues such as opposing gun control and supporting the Keystone XL pipeline to present himself as somewhat more moderate than many of his fellow Democrats and Montana's long-running tradition of ticket-splitting (while Tester is currently the lone Democrat in Montana's Congressional delegation; as recently as 2014 both Senate seats were held by Democrats) I think it's more likely Tester wins re-election than it would be for Cruz to lose re-election.