Nov. 5 (Bloomberg) -- Voter turnout for the 2008 presidential election that swept Democrat Barack Obama to the White House is likely to be the highest since Lyndon Johnson's landslide victory four decades ago once results are tabulated.

Obama won the highest proportion of the popular vote since Republican George H.W. Bush defeated Democrat Michael Dukakis in 1988. The 52.4 percent of the popular vote that Obama won -- 63.4 million ballots -- is the highest of any Democratic candidate since Johnson's 1964 victory.

It's likely that once the votes are counted, the election drew ``the highest turnout in 40 years,'' said Curtis Gans, director of the Center for the Study of the American Electorate at American University in Washington.

Obama is the first Democrat since Jimmy Carter in 1976 to win more than 50 percent of the popular vote. Bill Clinton was twice elected president without getting half of the popular vote. Obama's opponent, Arizona Senator John McCain, got 56 million votes, or 46.3 percent of the total, according to the latest figures.

This year's turnout rate will fall short of the record 67 percent turnout of eligible voters in 1960 and 64 percent in 1964, Gans said.

``It's been hyped as a record turnout and it ain't,'' he said. ``And it probably won't even be close.''

Popular Vote Total

So far, the popular vote total is 121 million. The vote total would have to reach 135 million to exceed the 1964 turnout, when Johnson beat Barry Goldwater, another Republican senator from Arizona, Gans said.

It would take 140 million votes this year to reach the 67 percent turnout recorded in 1960 when Democrat John F. Kennedy defeated Republican Richard Nixon, he said.

The final totals may not be known for six weeks as states finish counting and verifying the results, Gans said. For example, in California, the most populous state, 5 percent of precincts still haven't reported complete results.

Still uncounted are ``are a lot of absentee and mail votes'' from other states as well, including Oregon, Washington, Alaska, Ohio and Georgia, he said.

Estimates vary among voting-turnout experts of the number of ballots still uncounted. Gans estimated that 126.5 million to 128 million votes will have been cast when ballot counting is completed. Michael McDonald, a political scientist at George Mason University, estimated the total will reach 133 million.

Young Adults

Based on McDonald's estimate, the voting rate of young adults ages 18 to 29 increased 6 percentage points to 55 percent of their age group, according to Rock the Vote, a Washington- based non-partisan group that promotes voting by young people.

If 133 million people voted and young adults made up 18 percent of the electorate, then 24 million of them cast ballots this year, according to his estimate.

Exit polls show that young voters favored Obama over McCain by 66 percent to 32 percent. Therefore, young voters may have helped the Illinois senator win such closely contested states as Virginia, Rock the Vote said in a statement.

There has been a ``very large jump'' in voting by young adults in the last two presidential elections, said Peter Levine, an expert on youth voting at Tufts University's Center for Information and Research on Civil Learning and Engagement.

``It's not all Obama,'' he said. ``Some of it is young people quite independent of candidates. They are, relatively speaking, more idealistic and engaged and attentive to the news than Generation X was,'' said Levine, referring to people born between 1965 and 1980.

To contact the reporters on this story: James Rowley in Washington at jarowley@bloomberg.net; Christopher Stern in Washington at cstern3@bloomberg.net or +1-

Last Updated: November 5, 2008 18:33 EST