Let’s start today with Sean Trende — still the best name in forecasting — and his new Monte Carlo simulation. He has a sidebar explaining how those work, but let’s skip that for now and get to the meat of the matter:

I first looked at races The Cook Political Report currently rates as something other than “safe”; over the past 20 years, only two races that Cook Political has rated as “safe” at this point in the game have wound up switching hands, so we can be awfully confident that those seats are “staying put.” That leaves me with a universe of 17 competitive Senate races, 15 of which are held by Democrats, two of which are held by Republicans.

The next step is to total up our simulations, showing how frequently Republicans would win the Senate at each job approval interval for Obama.

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Gallup has Professor Wiggleroom’s current approval rating at 46%, which Trende rates as good for between 8 and 12 GOP pickups. Even the lower number is good enough to make Harry Reid the new minority leader, which would suit me like a Savile Row tailor.

The are caveats however. Notice that even at 46%, Wiggleroom’s numbers have been on the upswing. I attribute that to him staying out of the news lately, and to the feeling of national wellbeing we usually enjoy during the Olympics. Also note that Trende’s simulation puts the mostly likely Democrat loss at seven seats, which I read to indicate that each seat will be harder to win for the GOP than the previous seat. Or perhaps not, because a nine-seat gain is Trende’s second-most likely outcome.

The third caveat comes in three parts: Candidates, candidates, candidates. Mark Udall should be as good as gone here in Colorado, but our craptaculent state GOP can’t produce any top-tier statewide candidates.