At least in Iowa, and potentially in other locales in the heavily contested Midwest, the Des Moines Register’s endorsement of Mitt Romney shook up both campaigns. This was the most prominent, certainly left-of center editorial board (which had not endorsed a Republican since Richard Nixon in 1972) in a deadlocked state abandoning President Obama, whom it endorsed in 2008. The message both to voters and from voters (who reportedly influence the endorsement) was in effect: It’s fine to dump him. The editorial board issued a stunning rebuke to the incumbent president:

Barack Obama rocketed to the presidency from relative obscurity with a theme of hope and change. A different reality has marked his presidency. His record on the economy the past four years does not suggest he would lead in the direction the nation must go in the next four years.

Voters should give Mitt Romney a chance to correct the nation’s fiscal course and to implode the partisan gridlock that has shackled Washington and the rest of America — with the understanding that he would face the same assessment in four years if he does not succeed.

It is not clear whether Obama’s insistence (and then reversal) in having an off-the-record conversation with the editorial board figured into the decision. But it seems fortuitous that Romney chose to give his closing economic argument in Iowa on Friday.

In an era in which one can guess the endorsement of 90 percent of newspaper editorial boards (no matter how shabby their candidate’s performance has been), the Des Moines Register succeeded in injecting some genuine surprise. By going its own way, showing some independence from conventional center-left wisdom, it becomes the single most important editorial endorsement of the presidential race.

I asked Tim Albrecht, communications director for Iowa Gov. Terry Branstad (R), if a newspaper endorsement really packs any punch. He replied via e-mail late Saturday night: “If it was Obama, no. Since it’s Romney, this will send absolute shockwaves through this race.” He termed this a “big time” boost for Romney.

Perhaps readers on the fence in the state will be indifferent to the Des Moines Register’s endorsement. After all, newspaper endorsements generally have played very little difference in recent elections. But that is in part because they are so predictable and usually divorced from readers’ opinions. In this case the Des Moines Register’s editorial board acknowledged that readers’ opinions carried some weight. (“After watching the two candidates over the past six years, interviewing them both at least twice, researching their positions and the issues and having conversations with Iowans, the five of us [on the editorial board] spent more than two hours before reaching a consensus. It was a vigorous and useful debate.”) In other words, the endorsement is a reflection of where the race is in Iowa, as well as where the editorial board would like to see it end up.

The movement toward Romney in the upper Midwest is obvious. Wisconsin and Iowa are within the margin of error in public polling. In Minnesota, where Romney's decision to go up in the ads was promptly mimicked by the Obama camp, the last public poll is also within the margin of error. In sum, Obama’s Midwest “firewall” is aflame. While the pundits are fixated on Ohio, both campaigns know that Romney can win the presidency just as easily with two of three of Minnesota, Wisconsin and Iowa (throw in New Hampshire and Romney’s options expand even further.)

In pandering to his base this late in the race and going crass and super-negative, Obama is hoping to engage young voters and turn out core Democrats. But the price may be that in “nice” Minnesota and uber-polite Iowa middle-of-the-road voters get turned off or even disgusted. Sometimes having no positive message or lowering your rhetoric really does come back to bite you.