The Tea Party movement will rally April 15 in cities across the country, flexing physical muscle where — so far — it has not been able to have much impact politically.

As readers know, I’ve frequently defended the Tea Party push on the general principle that any honest dissent is healthy and on the particular principle that the movement’s initial objections to bank bailouts and alliances between the government and Wall Street were not just appropriate but necessary.

I attended a number of Tea Party rallies in the spring on 2009. Even then, I was uncomfortable with the manipulation of the movement by DC insiders associated with corporate front groups such as Americans for Prosperity and the uglier expressions of hatred toward President Obama by what was then a fringe element at the edge of the gatherings.

But there was something genuine about much of the initial Tea Party organizing. Citizens who were sincerely angry with their government were petitioning for the redress of grievances. I didn’t have to agree with them on every issue to think they were contributing something to the process.

Unfortunately, the movement has not been well served by the passage of time. It has been too frequently manipulated by Washington, D.C., insiders and political hangers-on like Sarah Palin — a supporter of the bank bailout and close ally of the Wall Street crowd — and has been defined more and more by hatred of Predident Obama and all things Democrat than a genuine populist fervor.

This has weakened the movement’s potential influence on a process that could use some shaking up, as has its inability, for the most part, to express itself electorally.

Tea Partisans like to claim that they elected Massachusetts Senator Scott Brown, the moderate, pro-choice Republican who won a January special election for a seat historically held by the Kennedys. That’s a stretch, as Brown’s Democratic opponent was agonizingly inept. More significantly, Brown has since his swearing in emerged as the most reliable Republican ally the Democrats have on spending issues — especially the extension of unemployment benefits. (Just this week, Brown provided another key vote to allow Democrats to break a GOP filibuster attempt.)

But at least the Massachusetts voting provided room to stretch. Since January, the Tea Party has had an exceptionally hard time achieving electoral traction. Candidates backed by the movement were pretty much wiped out in the Illinois and Texas Republican primary and runoff elections, where they challenged a number of Republican legislators and members of the U.S. House. And its supposed champions, like veteran Florida political player Marco Rubio, are now busy slathering themselves in precisely the sort of special-interest money that buys bank bailouts and corporate giveaways from Congress.

Even more unsettling — for those of us who held out a measure of hope that the Tea Party movement might actually develop an independent populist edge — is the circumstance in a number of states where old-school Republican insiders are trying to hijack the rebel spirit of the movement and use its energy to advance their own electoral agendas.

In Wisconsin, for instance, former Bush-administration Secretary of Health and Human Services Tommy Thompson, who went on to become a Washington lobbyist who secures lucrative federal contracts for his clients by working closely with the Obama administration and major government agencies, is set to address an Tax Day rally.

The Thompson-Tea Party pairing is only the most comic of a number of attempts by Republican insiders with close ties to Wall Street to turn the Tea Partisans into unquestioning followers rather than the sort of free-spirited political brigands who might actually change the course of human events.

The Tea Party movement will only have a meaningful impact on the Republican party in particular and our politics in general if it stays true to a set of core principles that are rooted in distrust not just of big government but of big banks and big business — and a healthy fear of those moments when all the bigs get together, as they did during the bank bailout fight.

In a very real sense, the question is whether the Tea Party movement will embrace the genuine dissents expressed by the likes of Texas Congressman Ron Paul, who for years has been raising the alarm about abuses by the Federal Reserve and the manipulation of trade policy by Wall Street, or the "I’m not a populist but I play one on Tax Day" manipulations of DC-insiders-turned-big-business-lobbyists like Tommy Thompson.

One does not need to agree with Ron Paul to know he is serious, and that his message is a potent one. By the same token, only a fool would think that marching in lockstep behind a member of George Bush’s Cabinet who now works as a lobbyist for some of the top recipients of government contracts in Washington is going to lead to any kind of change.