WASHINGTON — Democrats moved forward with plans to override President Bush’s veto of a $290 billion farm bill Thursday despite a printing error that has turned a triumphant political victory into a vexing embarrassment.

It seems that no one read the bill after it was printed on parchment paper and sent to the White House, where Bush vetoed it Wednesday. Missing was a 34-page section on international food aid and trade.

Democratic leaders in the House decided to pass the bill again, including the missing section in the version that Bush got. That vote was 306-110, again enough to override another veto from Bush should the need arise.

But Senate Majority Leader Harry Reid, D-Nev., saw little need for that and planned to go ahead with a vote on overriding Bush’s veto of a bill that is only 93 percent of what Congress passed. The House on Wednesday voted overwhelmingly, 316-108, to override Bush’s veto, even knowing that what he vetoed was not the complete bill that Congress passed.

If the Senate overrides Bush’s veto, all the other provisions of the bill except for the missing section on international food aid and trade would be law. That includes billions of dollars in new subsidies for farmers and increases in food stamps and other nutrition program for the needy amid rising grocery prices.

Still unclear Thursday was how lawmakers will deal with the missing 34-page section. The House Democrats planned to vote on passing that section again Thursday and send it to the Senate.

House Republicans used the error to plead Democratic incompetence. They said Bush vetoed a different bill from the one Congress passed, raising questions that the eventual law would be unconstitutional.

The White House also seized on the error.

“Maybe it gives them one more chance to take a look and think about how much they’re asking the taxpayers to spend at a time of record farm income,” said White House spokeswoman Dana Perino. “I think what this clearly shows is that they can even screw up spending the taxpayers’ money unwisely.”

Reid said the process is entirely legal.

“We have, under good legal precedent, going back to a case I understand in 1892 where something like this happened before, it is totally constitutional to do what we’re planning to do,” he said, without elaborating on the case.

Robert B. Dove, a former Senate parliamentarian, agreed.

“It really doesn’t matter what Congress actually does, all that matters is what goes to the president,” he said. “The courts don’t really want to get into the workings of Congress and try to figure out what the Congress really meant to do.”

But Republicans continued to berate Democrats over the mistake, delaying action by forcing the House into a vote over whether the Democrats should be investigated by the Committee on Standards of Official Conduct for abuse of power. The motion was dismissed on a party line vote.

“The House should not gloss over an incident of this magnitude,” Rep. Doc Hastings, R-Wash., said on the House floor. “It’s a serious constitutional violation.”

Bush says the legislation is too expensive and would send too much government money to wealthy farmers. A bipartisan group of negotiators on the bill made small cuts to subsidies to appease the White House, but Bush said it wasn’t enough.

The veto was the 10th of Bush’s presidency, but Congress had overridden him only once before, on a water projects bill.

Congressional Republicans overwhelmingly abandoned Bush in voting to override the legislation Wednesday, overlooking its cost amid public concern about the weak economy and high gas and grocery prices. GOP lawmakers are anxious about their own prospects less than six months before Election Day.

About two-thirds of the bill would pay for nutrition programs such as food stamps, about $40 billion is for farm subsidies and another $30 billion would go to farmers to idle their land and for other environmental programs.

The farm bill also would:

—Boost nutrition programs by more than $10 billion over 10 years and expand a program to provide fresh fruits and vegetables to schoolchildren.

—Cut a per-gallon ethanol tax credit for refiners from 51 cents to 45 cents. The credit supports the blending of fuel with the corn-based additive. More money would go to cellulosic ethanol, made from plant matter.

—Require that meats and other fresh foods carry labels with their country of origin.