With less than two weeks to go until the midterms, and with polls pointing to the prospect that Republicans could take control of the Senate, the stakes are high — not just for the Obama administration and congressional Democrats, but for the United States.

The consequences of Republican control of both the House and Senate could be catastrophic for the environment, workers, women and minorities.

Senate Minority Leader Mitch McConnell, R-Ky., promised a gathering of donors hosted by the Koch brothers that “We’re not going to be debating all these gosh darn proposals … things like raising the minimum wage … extending unemployment … the student loan package.”

And it won’t just be progressive proposals that are stymied. Consider the judges who will never make it to the bench, including the highest, when it is Sen. Chuck Grassley, R-Iowa, and not Sen. Patrick Leahy, D-Vt., who is in charge of the Senate Judiciary Committee. Consider the destabilizing political circus Republicans will create for the Obama administration and the nation when Rep. Darrell Issa’s hyper-partisan investigations into fake scandals spread from the House to the Senate.

If Republicans take charge of key Senate committees, they will restrict and remake the range of debate. What happens, for example, when Sen. Pat Toomey, R-Pa., formerly president of the right-wing Club for Growth, takes over Sen. Sherrod Brown’s subcommittee that oversees financial institutions and consumer protection? What happens to the Iran nuclear negotiations if McConnell, Sen. Lindsey Graham, R-S.C., and Sen. John McCain, R-Ariz., are deciding when to bring up a sanctions bill?

But a Republican takeover of the Senate is not a threat just because of what Republicans will do. Progressives also should worry about the many areas of potential agreement between the president and a Republican-controlled Senate.

It is Senate Majority Leader Harry Reid, D-Nev., for example, not Republicans, who is denying the president fast-track authority to force corporate trade deals through Congress. Without Reid in the way, “free-trade” pacts like Trans-Pacific Partnership — which labor leaders have called “NAFTA on steroids” — are likely to become the law of the land.

Likewise, President Barack Obama and Republicans could agree to pursue lower corporate tax rates — as opposed to infrastructure investments and job creation — as their primary economic-development initiative. And let’s not forget that Obama has repeatedly floated cuts to Social Security as a bargaining chip in negotiations with Republican leaders. Although we believe that the president has many progressive instincts, he has shown an inclination to seek consensus rather than to fight. If Republicans control both chambers of Congress, any consensus will err to the right.

Perhaps the most worrying consequence of a Republican-controlled Senate will be the extension of an already damaging austerity agenda. Working Americans, who have suffered through years of a stagnant economy, will see their livelihoods threatened by the shifting power dynamic in Washington.

Think, for example, about how different the next debt-ceiling fight will look. Republicans have repeatedly used the debt ceiling to hold the economy hostage, but each time they have relented for the same basic reason: the conclusion that it would be Republicans, not the president, who would be blamed for the consequences. After all, if Congress couldn’t get a bill to Obama’s desk, how could he be blamed for not signing it?

But if Republicans take the Senate, the calculus will change. House Speaker John Boehner, R-Ohio, and McConnell (if he survives the challenge by Democrat Alison Lundergan Grimes) will be able to send hundreds of bills to the president’s desk for his signature or veto. What happens when they send him a bill to prevent a default on our debt at the 11th hour, attached to a bill that ravages Social Security?

The Republican Party will gain the power to force the president to choose between impossible options.

It is with this sort of leverage that empowered Republicans will be able to attack key progressive priorities while advancing a right-wing agenda that includes the Keystone XL pipeline, a ban on abortions after 20 weeks, an assault on the rights of lesbians, gays, bisexuals and transgender people, the decimation of an already weak Dodd-Frank Act and more tears in an already weakened social safety net. This time, it might be Obama who shuts down the government.

In a democracy, there is no such thing as an election without consequences. Many progressives are not satisfied with today’s Democratic Party; they want it to be more populist and progressive. But they also know it is absurd to suggest that there are no differences between the two major parties, and it is madness to suggest that little will change if Republicans take the Senate.

A lot will change — and the change will be the worse for women, immigrants, workers and the environment. A Republican Senate, working with a Republican House, will be a wrecking crew. There is only one way to avert the devastation: Vote with a vengeance on Nov. 4.

Katrina vanden Heuvel is editor and publisher of the Nation magazine and writes a column for The Washington Post.