Dean Heller (R): 52 (37)
John Ensign (R-inc): 34 (45)
Undecided: 13 (18)
Dean Heller (R): 30
John Ensign (R-inc): 20
Sue Lowden (R): 12
Danny Tarkanian (R): 10
Sharron Angle (R): 9
Brian Krolicki (R): 6
John Chachas (R): 5
Someone else/Undecided: 8
(MoE: ±4.9%)
This is a pretty dramatic turnaround from the last time that PPP looked at the 2012 Republican Senate primary (which was released right after the November election, although I just noticed that the sample was taken before it). While the old poll had John Ensign looking surprisingly strong, this seems more in line with the conventional wisdom: that Ensign is toast, at least when matched up with GOP Rep. (and former SoS) Dean Heller. Ensign loses either as a two-way race or in a jungle-type configuration that throws in every possible GOPer. (Also noteworthy in the latter: Sharron Angle polls all of 9%, suggesting some serious buyer's remorse over having nominated her last year.)
I'm really not sure what (other than a very different sample composition) might have caused the sudden drop in Ensign's fortunes, since nothing has really happened to him in the last few months, but at any rate, he had a 64/23 approval (remember, among Republicans only) in October and now that's down to 53/30. Contrast that with Heller, who was at 56/8 in October and now is up to 63/12, suggesting he's getting better known without his negatives going up much, maybe consistent with people starting to pay more attention to the race and casting about for alternatives to the ethically-plagued Ensign. Given these numbers on top of Ensign's dried-up fundraising, it may truly be a short matter of time (as insiders expect) before Ensign announces he isn't running again.
As for a Democratic opponent, it'll be a while till we have a clear sense of that. Rep. Shelley Berkley has just announced that she's pushing back her timetable on making a decision about the race, to somewhere around "late spring or early summer." I've gotta wonder if she's waiting to see whether Ensign bails and Heller gets in without serious other GOP opposition, which might make the race much less appetizing to Berkley.