The Des Moines Register poll, conducted by the firm run by the respected local pollster J. Ann Selzer, has a history of accuracy. National Review’s Jim Geraghty dug into the archives to illustrate just how accurate:

The final Iowa Poll in 2012 gave Obama a 5 point lead. He won by 5.2 points.

The final Iowa Poll in 2010 showed heavily favored incumbent Sen. Chuck Grassley head by 31 points. He won by… 31.3 points.

The final Iowa Poll in 2010 for the governor’s race showed Terry Branstad winning by 12 points. He won by 9.7 points.

The political class places a fair amount of deserved weight on what Selzer’s surveys show, particularly her company’s final poll of the election cycle. On Saturday night, Selzer crushed the hopes of millions of Democrats when she determined that “this race looks like it’s decided,” and Joni Ernst is likely to be Iowa’s next U.S. Senator.

In early October, The Des Moines Register poll found the race for Senate in Iowa razor-tight. Ernst led Rep. Bruce Braley (D-IA) by just 47 to 46 percent. The race has since broken in Ernst’s direction; she has opened up a 7-point lead, with the support of 51 percent of Iowa’s voters to Braley’s 44 percent.

Braley’s position has deteriorated significantly from DMR’s last poll. The congressman is now losing in every congressional district in the state, including the one he represents in Congress. Braley led Ernst by 1 point in his home district in early October. Today, he trails Ernst by 3 points among his own constituents.

Candidates matter, and the DMR poll found that the campaigns waged by both Ernst and Braley had a significant impact on how Iowans will vote on Tuesday.

• The negativity in the race has hurt Braley more than Ernst. Forty-four percent say he has been more negative in campaign ads, compared with 32 percent for Ernst.

• Among several potential mistakes the two candidates have made, the one that stands out is Braley’s seemingly condescending remark about Republican U.S. Sen. Chuck Grassley. In March, GOP operatives released caught-on-tape remarks Braley made at a private fundraiser in Texas that seemed to question the qualifications of “a farmer from Iowa without a law degree” to become the next chairman of the Senate Judiciary Committee.

“He seemed to think it just didn’t matter,” Selzer said of Braley’s odd decision to cast aspersions on the state’s senior senator. “He never explained it.”

Selzer cautions that, while the race appears to be breaking for Ernst, “enormous resources” are being mobilized in order to save Braley from himself. What’s more, Republicans would be foolish to believe that this race is Ernst’s to lose. While DMR’s survey is the gold standard for Iowa surveys, no other poll has shown the Republican candidate with that strong a lead. In the Real Clear Politics average of polls, Ernst presently leads by 1.8 percent. Most of the polls in the field in October show the race is within those surveys’ margins of error. Democratic voter mobilization efforts cannot overcome a 7-point deficit, but they may be able to neutralize a narrow 1-point lead.

While Ernst’s people should not get complacent, the DMR survey is a good sign that fortune is going to be with their candidate on Tuesday.