If you think, as I’ve argued repeatedly, that we need a “radically centrist” third-party presidential candidate to shake things up, and to force both political parties to confront the myriad issues that their interest groups and ideological litmus tests bar them from treating honestly, then there are only two ways for that to happen in 2012. Like it or not, both depend on wealthy Americans investing in creative political change.

The first scenario is that the new group Americans Elect succeeds in securing ballot access in all 50 states and runs a national online nominating convention (in which every registered voter can be a delegate) next summer that will put an independent ticket on the ballot. The group tells me that it is on track to have ballot access in 27 states by the end of this year; by law, the other 23 don’t allow the relevant signature-gathering until next year.

The political establishment is seriously underestimating the potential of Americans Elect to become a disruptive force in our politics. When the day comes next year that the group announces it has ballot access in all states, the floodgates will open in terms of press, candidates and public interest.

But for now, AE still has its work cut out. It isn’t on the radar of most opinion leaders, let alone the broader public. The group ultimately won’t succeed without a major advertising campaign funded (as is its ballot-access drive) by wealthy individuals.

The second option is that a patriotic billionaire with the means to secure ballot access on his or her own pursues an independent campaign. (The tab is roughly $15 million to $20 million for the necessary lawyers and signature gatherers, I’m told. Then comes the much costlier national ad campaign to rival that of the two parties.)

As a practical matter, then, we won’t shake up our politics next year unless some wealthy patriots invest in a break-the-mold presidential campaign.

There is, of course, no guarantee that cash alone will give us the right stuff. What we need is a new and much improved version of what Ross Perot modeled in 1992. (I’m working on what the stump speech should sound like so that interested parties won’t have to start from scratch.) The bottom line is that radically centrist money is a necessary (if not sufficient) condition for making 2012 the year that kicks off the long-term project of American renewal.

Yet here’s the problem: Some wealthy patriots in the “far center” who might consider running for president or supporting such efforts think philanthropy is a better way to spend their time and money.

So as a public service, I want to explain why a presidential campaign is a much better investment.

Anyone who’s spent any time around foundations eventually realizes two things. First, there is no shortage of good works to be done, and foundations are doing plenty of it. Second, the impact of direct philanthropy pales next to the impact of shaping more effective and efficient uses of the vastly larger public resources available to government.

For this reason, farsighted philanthropists all come to realize that advocacy — i.e., efforts to shape how public resources are utilized — offers the best possible bang for the charitable buck.

So if the choice for a high-net-worth patriot is to devote himself or herself to a foundation, or to run for president or invest in related efforts, there’s no question that the presidential campaign is the path to greater impact.

That’s because there is simply no better vehicle for advocacy than a presidential campaign. It’s the moment every four years when the press and public are attuned to a broad discussion of the nation’s future. And with our two parties poised to run grossly misleading campaigns next year in their drive to win 50 percent plus one, the opportunity to break through with real answers and straight talk is enormous.

Nothing a foundation does through its own advocacy can compare with a presidential campaign’s ability to influence the debate. This is true even if that campaign doesn’t win, because the issues on which it educates and energizes the public — as with Perot and the deficit — get co-opted by the two parties.

Let me be clear: I’m not saying that Mike Bloomberg or Starbucks CEO Howard Schultz or others rumored to be weighing such steps are “the answer.” We’d need to know much more about their ideas for the country before making such judgments; and I expect more frustrated leaders will consider entering the fray in the months ahead.

But as Tom Friedman and Michael Mandelbaum argue in their essential new book, “That Used to Be Us,” the “shock therapy” the right independent candidacy could provide for our dysfunctional politics presents an unrivaled opportunity.

If you’re rich, serious about changing the world and think our two-party tyranny has become part of the problem, there’s no better time to invest in disruptive political innovation. The country you save may be your own.

Matt Miller is a senior fellow at the Center for American Progress and co-host of public radio’s “Left, Right & Center.” He writes a weekly online column for The Post.