If everyone voted, results would be ... the same?

Didn't make it to the polls? Don't beat yourself up. It's true – your vote doesn't matter.

OK, OK, maybe that opening is a little too provocative. Voting is an important act of citizenship. Casting ballots gives Americans ownership of their government. It legitimizes leaders and tells them where to steer the nation.

Furthermore, turnout for elections has dropped so low that vanishing voters have become a dire problem. A congressional primary determined by less than 10 percent of eligible voters isn't democracy. It's a lottery.

But here's the nut, as we say in the news biz: US politics might not be much different from today if turnout were 100 percent. That's the contention of some political scientists who study voting behavior, anyway.

If everyone eligible voted, the split between Democrats and the GOP might be about where is today. Al Gore would still be president.

(He's not? Well, we're talking popular vote totals here, not Electoral College.)

"Simply put, voters' preferences differ minimally from those of all citizens. Outcomes would not change if everyone voted," concludes a study by University of California political scientists Benjamin Highton and Raymond Wolfinger.

According to the research by Messrs. Highton and Wolfinger, Ronald Reagan would still have won reelection in 1984 and George H.W. Bush would still have won the White House in 1988 if every eligible US citizen went to the polls. Bill Clinton would also have won in 1992 and '96, albeit with slightly larger margins.

The population as a whole is indeed more liberal than voters on certain issues, such as government-paid universal healthcare and environmental regulations. But it is also more conservative on others, such as abortion and the role of gays in the military, claim Highton and Wolfinger.

Data produced by the University of Michigan's National Election Studies similarly show that the nonvoting population is difficult to peg, ideologically speaking.

The reason? Nonvoters themselves may be quite a diverse group. It is true that the poor, the less educated, and minorities are less prone to vote than rich, educated whites. But none of these groups, by themselves, constitutes a majority of nonvoters.

The most numerous nonvoters, by far, are young people and the transient. In the 1996 presidential election, 43 percent of those who did not vote had lived at their then-current address for two years or less. Thirty-three percent of nonvoters were aged 18 to 29.

"The nonvoters aren't who you think they are," says Wolfinger, who teaches at the University of California's Berkeley campus.

This conclusion is at odds with the conventional wisdom of political professionals, who have long felt that if the US had 100 percent turnout it would lurch sharply to the left.

This belief is based partly on polls that show Democrats do better if controls indicating whether a respondent is a likely voter or not are removed.

"The missing half of the electorate is not randomly distributed," says Micah Sifry, an analyst with the watchdog group Public Citizen. "It's disproportionately people of lower economic status."

The contention that universal turnout would bring in the Democrats for 100 years, to paraphrase liberal icon John Kenneth Galbraith, also stems from the fact that party pros are working in a different context from academics.

A shift of a few points may seem meaningless in the long run to political scientists. But in today's 50-50 nation, split almost evenly between Republicans and Democrats, such a shift might seem seismic in individual races. To see this, one has to look back no further than 2000. Turnout studies show that Democrats would have won the White House if everyone voted.

But in a statistical sense that would not really constitute a change – since Gore "won" in the sense that his popular vote total was larger than George W. Bush's, anyway.

There is also the question of whether universal participation would make campaigns and parties different. If everyone voted, the theory goes, parties might not focus so much on motivating their most partisan, core voters, as they do today.

"If you had anything close to 100 percent participation you would get a different kind of campaign," says Thomas Patterson, a professor at Harvard University's John F. Kennedy School of Government and author of the new book "The Vanishing Voter."