Scott Walker and Rick Perry. (Photos: Morry Gash/AP, Sid Hastings/AP)

The conventional wisdom about the Supreme Court’s controversial 2010 Citizens United decision was that it would usher in a dark new day in politics when billionaires would be able to prop up their favorite candidates — and perhaps even propel them all the way to the presidency—by funneling unlimited amounts of money to the shadowy groups known as super-PACs.

And yet despite dire predictions from critics, including the current occupant of the Oval Office, the first two Republican candidates to drop out of the 2016 nominating contest were two of the party’s biggest super-PAC beneficiaries: Texas Gov. Rick Perry, whose super-PAC supporters raised nearly $17 million through the end of June, and now Wisconsin Gov. Scott Walker, who was backed by a pair of super-PACs that had raked in a staggering $26 million.

What gives? Does the recent demise of the Perry and Walker campaigns mean that super-PACs aren’t as “super” — or as dastardly — as the Washington naysayers seem to think?

There’s certainly something to the idea that the power of super-PACs and their billionaire boosters has been overstated — especially when it comes to a presidential race. The Perry and Walker campaigns prove this point.

Of the $17 million raised this cycle by a trio of Perry-friendly super-PACs — Opportunity and Freedom, Opportunity and Freedom I and Opportunity and Freedom II — at least $15 million came from just three ultrawealthy donors.

Two were Texans: Darwin Deason, the retired founder of a data- processing computer company, wrote a check for $5 million; Kelcy L. Warren, oil-pipeline magnate, chipped in $6 million. A third, anonymous supporter gave the remaining $4 million.

Similarly, three megadonors were responsible for half of Walker’s super- PAC haul: Wisconsin roofing billionaire Diane Hendricks and TD Ameritrade founder Joe Ricketts forked over $5 million apiece, while Liz and **** Uihlein, co-founders of the Wisconsin-based manufacturer Uline, shelled out another $2.5 million.

The plan, as Politico recently reported, was for the super-PACs to “absorb many of the core functions of the campaigns during the early months,” giving the candidates “the time and space to do the type of traditional retail politicking necessary to gain traction with the regular voters and small- to medium-dollar donors who traditionally powe[r] campaigns.” The pro-Perry PACs put paid organizers on the ground in Iowa; the main pro-Walker group launched a $9 million advertising campaign there as well.

But all of that outside money wasn’t sufficient, on its own, to keep Perry and Walker afloat. The problem? Neither of them were particularly good campaigners — or fundraisers. (The two phenomena are, of course, closely related.) Rank-and-file Republicans weren’t eager to give Perry a second chance after his disastrous 2012 performance, and they soured on Walker, who soared in the early Iowa polls, when they saw what a dismal debater he was. And so Perry pulled in an anemic $1.1 million in direct campaign donations — total — before bailing earlier this month. Walker raised more, but not nearly enough to sustain his bloated 90-person payroll or make one last stand in the all-important Hawkeye State.

In that sort of situation, there’s only so much a super-PAC can legally do. They can’t coordinate messaging with the campaign. They can’t pay rent, phone bills, salaries, airfares or ballot-access fees — the basic, day-to-day expenses of running for president. And they actually have to pay higher rates than the official campaign to advertise on television or radio.

The strength of the super-PAC, in other words, is limited — especially when the candidate isn’t keeping up his or her end of the bargain.

This should come as a relief to critics who once worried about billionaires buying the White House. As former George W. Bush press secretary Ari Fleischer recently put it, the end of the Walker and Perry campaigns is “healthy because super-PACs alone should not keep candidates in the race if they can’t stay in by themselves. There is something democratic about grassroots, widespread money support. There is something antidemocratic about one person propping up a candidate who can’t make it.”