Plenty of liberals and other Americans of good conscience no doubt breathed a sigh of relief when AmeriTrade founder and Chicago Cubs co-owner Joe Ricketts distanced himself yesterday from the $10 million racially-tinged Jeremiah Wright ad blitz that the New York Times had reported he was considering buying. But it would be a mistake to consider that any sort of significant victory against the disproportionate power wielded by super PACs. Indeed, even if big donors decide not to corrode the atmosphere of the presidential campaign, they have already demonstrated—Ricketts did so earlier this week, in fact—their commitment to influencing state and local elections.  And it’s precisely in those elections—elections that many of us won’t be paying attention to—that their power over national politics will prove most decisive.

Take Tuesday’s Republican Senate primary in Nebraska, for example. From a national point of view, this was a relatively obscure affair: For many pundits, the only thing they knew about surprise winner Deb Fischer is that she was endorsed by Sarah Palin. Indeed, there was an initial tendency to push the Nebraska contest into the familiar template set a week earlier by the Mourdock/Lugar primary in Indiana: Conservative insurgent beats moderate. This had the advantage of pleasing the otherwise embarrassed conservative activists who had poured much time and treasure into the campaign of third-place finisher Don Stenberg. Democrats also had an interest in reinforcing that interpretation; the more Fischer looked like 2010 wacko Senate candidates Sharron Angle and Christine O’Donnell, the better the fundraising environment for Democratic candidate Bob Kerrey.

But this early conventional wisdom was wrong: A closer look shows that Fischer is a fairly conventional Republican politician, and ideology played little role in the primary’s outcome. (In part because all three major candidates constantly claimed to be true conservatives battling the ever-traitorous RINOs of the national party). A Public Policy Polling survey on the eve of the primary (which pretty much nailed the results) showed that so-called establishment candidate Joe Bruning’s shaky favorable ratings were actually highest among self-identified “very conservative” voters, while moderates felt most fondly towards Fischer.

But even if Fischer never makes it to Washington, this week’s election may have been one for the history books. That’s because what happened in Nebraska is the clearest example yet of what a post-Citizens United landscape is like, and an object lesson in the power of super PAC donors.

What this primary was about wasn’t ideology, but money. One prominent conservative gabber, the Washington Post blogger Jennifer Rubin, pointed to Bruning’s large advantage in funding over Fischer, and suggested her victory showed that “money is overrated.” Others (including PPP’s Tom Jensen and yours truly) looked at the large quantity of “independent” money—particularly from the Club for Growth and Jim DeMint’s Senate Conservative Fund—that was spent attacking Bruning and boosting the hapless Stenberg. Seen in this light, the contest was a money-driven murder-suicide affair, where the two better-financed candidates destroyed each other and left Fischer unscathed to pick up the pieces.

But on the ground in Nebraska, it was Ricketts’ last-minute brace of ads that was actually much more decisive. The ads—one boosting Fischer, one blasting Bruning—represented the kind of strategic, last-minute super PAC ad blitz funded by a single donor that Citizens United encouraged . To be sure, compared to huge individual super PAC investors like Sheldon Adelson (who single-handedly bankrolled Newt Gingrich’s Winning Our Future PAC) or huge super PACs with multiple investors (like Karl Rove’s Crossroads GPS, which has just launched a $25 million anti-Obama ad blitz in battleground states), Ricketts made a relatively modest investment of $200,000. But he made it in exactly the right place at exactly the right time.

TNR contributor Jonathan Bernstein best captured the lesson learned from Ricketts’ intervention in the Nebraska race:

Outside money matters more in Congressional races than presidential, and more in primaries than general elections. … And as we’ve just discovered, a single donor can be responsible for the election of a general election Senate candidate — or even, if Fischer wins, a Senator.

Why is that so? Paid media ads matter most in contests with three factors. First, where candidates are not as well known—this is true in down-ballot races, rather than presidential elections, since the public’s perceptions of Romney and Obama are already largely fixed. Second, where factors like party affiliation are less dominant—this points to primaries where candidate allegiance is far more fluid than in general elections. And third, where the cost and scope of advertising provides the greatest bang for the buck—this points to states like Nebraska and many others where you can get your message in front of a large percentage of voters for just $200,000.

This week’s primary contest in Nebraska had all three of these factors, but so will many other contests in the future. Political pros advising politically ambitious tycoons in the months and years ahead will likely use Ricketts’ intervention in Nebraska as an example of exactly the right way to make a big mark in an unregulated system of campaign finance.

Does this mean that big donors don't have an impact on presidential elections? Not exactly. Yesterday’s furor over Ricketts’ potential Jeremiah Wright ad proved another important point about the impact of rich individual donors in a post-Citizens United world: They don’t have to write a check to have a big impact, even on a presidential general election contest. They just have to clear their throats.

But ultimately, it’s Ricketts’ more quiet intervention in the Nebraska primary that may prove more effective and instructive. After all, it may have provided us with a new United States Senator. And it may have confirmed the most indulgent vanities of the very rich: That they’re invited not only to have a say in our political process, but the final word.

Ed Kilgore is a special correspondent for The New Republic, a blogger for The Washington Monthly, and managing editor of The Democratic Strategist.