When, after two excruciating months of headline-making negotiations, congressional Democrats and Republicans agreed to reduce projected increases in federal spending somewhat in return for a $2.1 trillion extension of the nation's credit line, a broad swath of the professional left knew whom to blame: the Tea Party movement.

"Tea Party Republicans have waged jihad on the American people," wailed New York Times columnist Joe Nocera. "This small group of terrorists have made it impossible to spend any money," complained Rep. Mike Doyle (D-Pa.). Salon's Michael Lind warned that "neo-Confederate" Tea Party "fanatics" were threatening to "destroy America's credit rating unless the federal government agrees to enact Dixie's economic agenda." Not to be outdone, former Vice President Al Gore called on Americans to emulate revolutionary freedom fighters in the Arab world.

"We need to have an American Spring," Gore said on Current TV, "a kind of an American nonviolent change where people on the grassroots get involved again. Not the, you know, not in the Tea Party style."

It takes a special kind of brain to advocate regime change against a force that controls neither the White House nor the Senate, let alone to react to a grassroots movement by lamenting the lack of a grassroots movement. Still, Gore was almost onto something: The Tea Parties hold an important lesson for left-of-center grassroots political activists. But to learn it, they have to get past their hatred of the Tea Parties.

House Speaker John Boehner (R-Ohio), who successfully steered Republican negotiations so that no taxes were raised in the debt-limit deal, is anything but a fiscally responsible, government-limiting public servant. He championed such Bush-era white elephants as No Child Left Behind, the single biggest increase in federal education spending in history, and Medicare Part D, which gave heavily subsidized prescription drugs to seniors. He supported George W. Bush's $100 million stimulus plan in 2008, his $700 billion Troubled Asset Relief Program (TARP) later that year, and his $1 trillion-plus war expenditures. As recently as last fall's congressional campaign, Boehner was explicitly refusing to contemplate cuts in military and entitlement spending—the two biggest growth engines in government.

What changed Boehner's tune? The Tea Parties.

In the run-up to the November 2010 elections, Boehner, along with his Senate counterpart, Minority Leader Mitch McConnell (R-Ky.), refused to include a Tea Party–backed ban on earmarks in his flaccid "Pledge to America" manifesto. Hours after the Republicans took over the House of Representatives, both men reiterated their opposition to a ban on legislative pork.

Not satisfied with merely winning elections, Tea Party activists flooded congressional phone lines and prodded the 90 new Republicans on Capitol Hill to face down a GOP leadership more concerned with appearances than reform. Amazingly, by February 2011, Boehner had caved under the pressure.

Even elected politicians are finally realizing what has been increasingly obvious since public opinion rose up in revulsion against the panicky TARP spending in the fall of 2008: The American public in general, and Tea Party activists in particular, are allergic to Washington's perennial prescription of increased spending and centralization for every real and imagined economic ill.

On nearly every occasion during Barack Obama's presidency when voters have had a chance to vent at their elected representatives on the issue, they have. In May 2009, Californians overwhelmingly rejected the elite consensus's tax-increasing package of ballot initiatives to fix the state's dire budget crisis. That summer, voters literally screamed at their congressmen about what would eventually become ObamaCare. In January 2010, a relatively unknown Republican won Teddy Kennedy's old Senate seat in Massachusetts, where Democrats outnumber Republicans by 2 to 1. And in November 2010, Tea Party activists not only helped Republicans recover control of the House but did so in many cases by backing candidates more radical than the ones favored by the GOP establishment.

Mitch McConnell may still lead Republicans in the Senate, but it's politicians like Rand Paul (R-Ky.)—elected with Tea Party backing over McConnell's hand-picked candidate in his home state—who represent the future. Clearly aware of this, Boehner and McConnell have been frantically remaking themselves as champions of limited government.

The success of the Tea Party movement offers the left a blueprint for change. For decades politicians like Boehner trampled on the conservative tradition of limited government. Obama and the Democratic establishment likewise have disrespected several core traditions of the American left. The best way to reassert those values is not by staying on the Democratic reservation but by refusing to be taken for granted.

In this month's cover story, Senior Editor Jacob Sullum provides a detailed explanation of how Barack Obama, whose pre-election signals on drug policy seemed promising, has turned out to be just as bad on this issue as George W. Bush. Obama's record has been particularly egregious with respect to medical marijuana, which he promised to tolerate but has instead tried to suppress at least as aggressively as his predecessor did.

The continued crackdown demonstrates the futility of elevating political parties and their candidates over single issues. Consider that three of the biggest supporters of the Democratic Party since the end of Bush's first term have been George Soros, Peter Lewis, and John Sperling—who also happen to be three of the country's most generous supporters of drug policy reform.

Soros in particular is a case study in how giving blanket support to a political party can undermine your favorite causes. According to a 2004 New Yorker article about anti-Bush billionaires by Jane Mayer, Soros' bill of particulars against Obama's predecessor included Bush's attempts to spread democracy at gunpoint, his expansions of presidential power, and his prison camp in Guantanamo Bay. In every one of those areas, as in the drug war, Obama has not been significantly better than Bush.

Politicians who can take supporters for granted will do precisely that, particularly when taking supporters' issues seriously would require upending the status quo. Although last July's debt deal did not cut a single dime from the federal budget, it did hold the line on taxes and reduce projected growth in spending. Even those modest accomplishments would have been impossible without the Tea Party's influence. Yet in the heat of the battle that preceded the deal, both Sen. John McCain (R-Ariz.) and the Wall Street Journal editorial page mocked Tea Party activists as "hobbits" oblivious to the real-world consequences of their actions.

The Tea Party movement was able to grind the gears of politics as usual by demonstrating to the McCains of the world that single issues matter more than whether the opposing party might win this or that congressional seat. As Eric Sterling, president of the Criminal Justice Policy Foundation, told Sullum, Obama has been able to pursue the war on drugs as usual partly because "those who care have not made him pay a political price yet."

Full marijuana legalization is likely to be on the ballot of at least a couple of Western states in 2012. An open question to drug policy reformers contemplating independence from the Democratic establishment at this moment of truth: If not now, when?

Matt Welch (matt.welch@reason.com) is editor in chief of reason and co-author of The Declaration of Independents: How Libertarian Politics Can Fix What's Wrong With America (PublicAffairs).