"What did he know, and when did he know it?" That's become the standard question to ask about presidents brushed with scandal.

But results of a new poll suggest that we should be asking a different question: "What does the average voter know, and why does he or she know so little?"

Don't get us wrong. We aren't primarily blaming the public. In fact, the survey of public knowledge about the presidential candidates and issues points toward other culprits -- television and the news media overall.

The nationwide telephone poll of 600 likely voters found them to be inundated by the media. Most said television is their main source of information, and the majority reported watching a TV news program virtually every day. Most also said they regularly read a newspaper.

It's not that the public is totally uninformed. ``Selectively misinformed'' would be more accurate. The more trivial the information, the better the media seem to be at communicating it.

For example, 86 percent of the voting public knows that the Bush family has a dog named Millie, and 89 percent could identify Murphy Brown as the TV character criticized by Vice President Dan Quayle.

In sharp contrast, only 19 percent could identify the Reagan Cabinet member recently indicted in the Iran-Contra scandal: Caspar Weinberger.

Even on an issue that intensified the week the poll was conducted -- with George Bush vetoing legislation to enact sanctions against China because of human-rights abuses -- much of the voting public is out of the loop. Almost as many people believe Bush imposed sanctions on China as know his actual position: retaining China's most-favored-nation status.

The new survey -- set for release Oct. 19 by Fairness & Accuracy In Reporting, the media watch group with which we are associated -- went beyond typical mass media polls. Besides asking voters for their opinions, it also probed for what information, if any, shaped those opinions.

The answers are hardly encouraging to those who hope for an informed electorate. If you're a media strategist for Bush, however, you might take solace that, despite your candidate's standing in popularity polls, some of your most ferocious, and distorted attacks are getting through to voters.

On the "tax and spend" theme, voters hold many misconceptions that favor the Bush campaign. Thirty-two percent answered that Arkansas state taxes are "among the highest in the nation," compared with only 21 percent who responded correctly that taxes in Gov. Bill Clinton's home state are among the lowest.

As to whether Congress spent more or less money last year than requested by Bush in his budget, only 22 percent answered correctly that Bush's budget called for more than Congress actually spent. Three times as many people (66 percent) answered inaccurately that Congress was the bigger spender. Blame national news media for ignorance of this fact.

Professors Justin Lewis and Michael Morgan, who supervised the poll in collaboration with the University of Massachusetts Center for the Study of Communication, say their findings contradict claims of a "liberal media" biased against the GOP.

"Many voters have absorbed deceptive Republican attacks against Clinton," Lewis and Morgan conclude. "It's due in part to news media emphasis on reporting campaign rhetoric rather than the facts, and their reluctance to focus on the record rather than on `claims' about the record."

The survey reveals deep ignorance among voters on basic subjects, such as how the federal government spends tax money. Asked whether more money goes to "foreign aid" or "the military" or "welfare," 42 percent selected foreign aid, which accounts for only 1 percent of spending. Almost a third of the respondents chose welfare, which is just 5 percent of the federal budget.

The correct answer is military spending -- more than four times larger than federal welfare spending. It was chosen by a mere 22 percent of those responding.

Heavy TV news viewers were the most uninformed about federal spending, as were Bush and Ross Perot supporters. Professors Lewis and Morgan attribute the misconceptions to intensive coverage of the "welfare problem" and foreign aid and to reporting on military spending that emphasizes cutbacks and job losses.

Whatever the particular explanations for the various incorrect answers, the survey as a whole indicates that the problem is more serious than simple ignorance.

As columnist Walter Lippmann once wrote, "Misleading news is worse than none at all." In 1992, thanks in part to mass media, much of what Americans "know" just isn't so.