Voting in Republican primaries and special elections showed what happens when moderate Americans stay home or react to the barrages of fear and intolerance. We end up with fringe candidates like Christine O'Donnell in Delaware and Sharron Angle in Nevada. Establishment candidates then spout the same disturbing ideas. (Witness Representative John Boehner, the House minority leader, trying to act like an outsider after 18 years in the Washington power elite.)

Democrats have been far too timid to argue the case, but they, and President Obama, have done many important things in the last two years.

Most important, the stimulus — which Republicans made sure was smaller than it should have been — saved the country from a deeper, more destructive recession. That is not a lot of comfort for the millions of unemployed Americans, but it would have been far worse if the Republicans had had their way. They have even opposed extending federal unemployment benefits.

American troops are coming home from Iraq. For the first time, troops in Afghanistan have the full backing of the White House and Pentagon. The United States is regaining the respect of allies around the world.

The Republicans have been rewriting history. They claim Mr. Obama's economic policies are a failure and hope Americans will forget that it was President George W. Bush who turned big budget surpluses into huge deficits and whose contempt for regulation ultimately brought us to the brink of financial collapse. The Republicans want to go back to more tax cuts for the rich and more free passes for Wall Street and big corporations.

Tea Party candidates are particularly worrisome. Some want to privatize Social Security. Others want to eliminate Medicare. Betting on the Republican establishment to temper these excesses is a bad bet.

Here are some things to bear in mind on Tuesday:

• Since Mr. Obama was elected, millions of poor children who did not have health insurance got it. A reform law was passed that already allows young people to be on their parents' plan until they are 26, bars insurers from dropping coverage after a beneficiary becomes sick, and removes lifetime caps on coverage. In 2014, many more benefits will kick in.

Republicans are determined to undo that progress. It would be a disaster. The law is the best chance in years to provide health insurance to the rapidly rising numbers of uninsured and to begin trying to slow cost growth in medical care and insurance.

• The country needs tax reform that is fair and doesn't get us even deeper in the red. Republicans are interested only in one thing: permanently extending tax cuts for the rich, adding $700 billion to the deficit over the next 10 years.

• The country needs jobs and to be globally competitive. Republicans are determined to block Mr. Obama's sensible proposals to create good jobs by rebuilding fraying infrastructure or creating new energy industries.

• The country needs sound regulation. If there is any doubt about that look at the oil spill in the Gulf of Mexico. Or the bank bailout that — despite what the Republicans are saying — happened on Mr. Bush's watch. The Republicans want more heedless deregulation.

• With very few exceptions, Republican candidates are hostile to the administration's efforts to address climate change and reduce the nation's dependence on fossil fuels. There has already been talk on Capitol Hill of stripping the Environmental Protection Agency of its authority to regulate greenhouse gases.