John Ensign could be vulnerable in a primary in 2012 but he actually has pretty solid approval numbers with Republican voters, suggesting that it would take a strong foe for him to be denied renomination.
64% of GOP primary voters in Nevada approve of Ensign's job performance to only 23% who disapprove. He's particularly strong with conservative voters who give him a 71/16 approval spread. That means any challenge to him is much more likely to succeed on ethical grounds than ideological ones- voters on the right flank of his party are a lot more comfortable with him than centrists.
Despite his relatively strong approval numbers he's held under 50% in a hypothetical primary campaign against Congressman Dean Heller. Ensign leads but only by a 45-37 margin. That may be more a reflection of Heller's remarkable popularity than a particular desire to replace Ensign- 56% of primary voters view Heller favorably to only 8% with a negative opinion- there aren't a lot of politicians you see these days with a 7:1 favorability rating even if it is just within their own party.
What may be particularly fortuitous for Ensign is that with voters who know Heller- whether they have a positive opinion or a negative one- Heller holds a 53-37 advantage. That could bode poorly for Ensign if Heller enters the race and starts catching up on the name recognition front.
The bottom line: Heller certainly could beat Ensign but it wouldn't be a slam dunk and he has to decide if he's willing to give up a relatively safe House seat to try for that.
Ensign does better against another potential primary challenger, Lieutenant Governor Brian Krolicki, leading him by a much wider 55-27 margin. Like Heller, Krolicki has solid favorability numbers at a 45/9 spread. But 46% of Republican primary voters don't know enough about him to have formed an opinion and that anonymity is holding down his overall numbers. Krolicki might have less to lose in a possible campaign than Heller though since he's not up for reelection in his current office until 2014 now.
I would not take it for granted that Ensign is dead in the water for reelection, either in the primary or general. He certainly might lose but there are a lot of other Senators without his personal baggage who have far worse approval numbers and David Vitter's resounding reelection in Louisiana last week showed voters are willing to put that stuff aside if they feel one of their officials is otherwise doing a good job. It'll be interesting to watch.
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