Editor’s Note: Each week we repost an excerpt of Katrina vanden Heuvel’s column on WashingtonPost.com.    You are a progressive voter, and you are disillusioned. So much so that you are thinking of sitting this election out.

Well, think again. Take a deep breath—then eat, pray, vote.

It’s true that the progress made by this White House—including passage of landmark health-care and financial-reform legislation and a stimulus bill that mitigated the impact of the recession—is too limited. And there have been some real disappointments: Tapping Wall Street insiders Larry Summers and Timothy Geithner to lead an economic team tasked with a Main Street recovery. Tepid advocacy for a public option and zero consideration for single-payer health care. Failure to aggressively take on too-big-to-fail financial institutions. And an Afghanistan surge instead of a needed exit strategy.

It’s no wonder so many progressives have demobilized. Note to politicos: If you diss your base, your base might just diss you, too.

But progressive apathy will hand right-wingers a victory. The Tea Partyers and House Speaker-in-Waiting John Boehner will gladly fill the void, fostering anger and division. Witness the Tea Party victories in last week’s Republican primaries, and listen to Boehner’s subsequent statement that their supporters "can drive this town to do the right thing for the American people."

When these guys are running the show, it’s not disappointment you will feel—it’s despair.

Why? Because far-right conservatives are ready to roll back many of the civilizing advances of the 20th century, including Social Security, Medicare and Medicaid. Republicans are also gunning to repeal and replace President Obama’s health-care overhaul—and the 20 or so states already fighting to overturn health-care reform in the courts would be emboldened by a Republican victory. Meanwhile, according to Bloomberg, "Wall Street is preparing for a Republican surge in Congress that could help it block proposed taxes on banks and investments, blunt new financial regulations and regain some of the lobbying firepower it lost."

These prospects should concentrate the mind. This is indeed a choice election. We’re not talking about a simple change of power in Congress, we’re talking about a fundamental reordering of America in terms of its priorities and possibilities.

Of course, there is an alternative. Rather than sitting out, progressives can sit in. We can channel our disappointment and anger (and fear of a GOP takeover) into organizing and campaigning for the principles we believe in, as the One Nation march on the Mall in Washington will seek to do on Oct. 2. After all, the change we seek isn’t going to come through one election, or one president. It will come from building coalitions, supporting progressive candidates and organizing independently.

The administration also needs to step up and rally its demoralized base. President Obama’s appointment of Elizabeth Warren to run the Consumer Financial Protection Bureau is a great start, though the president should relish a confirmation fight in the Senate, not avoid it by keeping her on as a special adviser.

The Democrats should also welcome a debate with Republicans on ending the Bush tax cuts for those making more than $250,000 a year. This is an issue that demonstrates which party is still in the pocket of Wall Street, and which is willing to extend at least some effort on behalf of a struggling middle class. It also exposes the hypocrisy of Republicans who rail against the deficit but would add nearly $4 trillion to it—at least twice as much as any program Obama has passed or proposed—to cater to their wealthy base.

And now, in this last stretch before November, comes a moment for Obama to lay out plans to rebuild America that show his fighting spirit, his moxie and his empathy—so he can connect in visceral ways with people who are angry, anxious and frustrated. As Thomas Geoghegan writes in The Nation, ideally these plans would be simple and universal—such as putting a usury cap of 16 percent on credit cards, establishing small government-run banks geared toward small-business lending, or extending Medicare to people reaching age 55.

So the big question facing progressives in these weeks before the midterm elections is this: Will we build on a politics of change? Or will we sit back and retreat because things haven’t gone as we had hoped?