What The Hell Is Happening In South Dakota?

The current state of the Senate races:

Senate Map

South Dakota has become a three-way race between Democrat Rick Weiland, Republican Mike Rounds, and Independent Larry Pressler. Aaron Blake summarizes a poll that came out yesterday:

A new poll of the South Dakota Senate race shows former three-term GOP senator Larry Pressler, now running as an independent, has surged into second place and is within the margin of error against former governor Mike Rounds (R). The poll, from automated pollster SurveyUSA, shows Rounds at 35 percent, Pressler at 32 percent and Democrat Rick Weiland at 28 percent.

Silver finds that this “is a challenging race to forecast — both because of the inconsistent polling and the three-way dynamic”:

But the logic programmed into the FiveThirtyEight model is as follows: because Pressler is more ideologically similar to Rounds than Weiland — at least according to the statistical measures that we use — the model assumes that Pressler and Rounds will mostly trade votes with one another rather than with Weiland. In other words, Pressler’s gains will tend to come at Rounds’ expense, and vice versa. (See here for a more technical explanation.)

That makes Pressler the more likely candidate to pull off the upset; he can gain ground relative to the frontrunner more quickly. The FiveThirtyEight model currently gives Pressler a 9 percent chance of winning the race, versus 3 percent for Weiland. Those chances will grow if more polls come along with results like SurveyUSA’s.

Alex Altman looks at Pressler’s ideology:

Pressler says he hasn’t decided which party he would caucus with if elected. But with the GOP’s lurch to the right, the former moderate Republican now sounds more like a Democrat. He voted for Barack Obama. He supports balancing the budget in part by raising taxes on millionaires, a new gas tax and the elimination of some corporate deductions. He wants to raise the minimum wage and teacher salaries, supports gay marriage, and says the U.S. should pare back its military spending. “I’m not an isolationist,” he adds. “I know we have to do some bombing.”

Kyle Kondik notes the cash Democrats are putting into the race:

The Democratic Senatorial Campaign Committee — which had seemingly written off this race — entered the race with guns blazing on Wednesday: Bloomberg reported that the DSCC will put $1 million in South Dakota in the final weeks of the campaign, mostly on television advertising to attack Rounds with the hope that Weiland or Pressler — who endorsed Obama in 2008 and 2012 — will prevail and then caucus with the Democrats. It also remains possible that one or the other will stop campaigning and endorse the other, which would really put Rounds in a bind.

Jonathan Bernstein disagrees. He figures, “If Rounds found himself in a head-to-head match with Pressler, he could unleash negative ads until Election Day with little worry about a backlash”:

The real danger for Rounds is that multicandidate races tend to be unstable. If Rounds attacks Pressler, Weiland might benefit; if Rounds attacks Weiland, Pressler might move up. Indeed, if Democrats believe that Pressler might caucus with them, the best play could be for Weiland to throw as much mud as possible at Rounds, in the hopes that both would be destroyed.

Nate Cohn is wary of making any predictions:

[T]he biggest reason to be cautious is that three-way races are particularly unpredictable. Fairly significant polling errors occurred in the three 2010 three-way statewide contests (defined as a contest in which three candidates entered Election Day with at least 20 percent of the vote in most polls). In governors’ races in Rhode Island and Maine, the error averaged about 8 points; in Alaska, the majority of pre-election polls showed Joe Miller in the lead, but Lisa Murkowski prevailed by about four points.

With this history and the race beginning to attract national spending, it wouldn’t be wise to dismiss anyone’s chances.