Tom Bradley, the Democratic candidate for governor, received almost 20,000 more votes than Republican George Deukmejian from those who actually went to the polls last November, according to figures released by the California secretary of state's office.

Yet today Deukmejian, not Bradley, sits in the governor's chair, the victor by 93,000 votes out of nearly 8 million cast and the beneficiary of a ballot-by-mail revolution so stunningly successful it has drawn the attention of political organizers throughout the country.

Through an unprecedented Republican mailing plan and state election law changes, which Democrats had supported, Deukmejian collected 302,343 absentee votes in November.

This was 113,231 more absentee votes than Bradley received, obliterating Bradley's 19,886-vote victory over Deukmejian among those who went to the polls.

"It just killed us," said Bert Coffey, California Democratic Party executive committee member, who watched Bradley lose a race nearly everyone thought he had won.

The percentage of absentee ballots jumped so suddenly, to 6.5 percent of the total vote compared with 4.4 percent in the governor's race in 1978, that election-night exit polls were thrown askew and most of the state's major pollsters incorrectly projected a Bradley victory.

Officials of both the Democratic and Republican National committees say they are studying the California results and the absentee ballot laws in other states to see if such a campaign can be pursued nationwide. California Democratic Party Chairman Peter Kelley is organizing a task force to consider how to use the same weapon.

"There is no question that one of the things we learned in California is that we are going to have to be more aggressive with absentee ballots," said Ann Lewis, political director of the Democratic National Committee.

According to Lewis, studies indicate heavy absentee voting favors incumbents, followed by candidates with strong ties to senior citizens, Republican candidates, and candidates with strong ties to students.

Some Democratic Party organizers point out that absentee voters are often businessmen who travel frequently and who tend to be Republicans.

Coffey said the benefits Democratic candidates might receive from such a campaign might not justify the cost.

However, John Meyers, executive director of the California Republican Party, said that the fund-raising appeal included in last year's absentee ballot mailing raised $288,000 for the state party, almost enough to pay for the absentee ballot campaign itself.

Meyers said he and other Republicans were philosophically opposed to the changes in the law that helped their campaign succeed, but once they were on the books, they saw no reason not to use them.

"The Democrats seemed to forget they were there," Meyers said. "But we're elephants, and we don't forget."

With a special $350,000 budget, the state Republican headquarters mailed 2.6 million special packets to all California households with at least one registered Republican two months before the November elections.

Each envelope contained a letter from President Reagan, a letter from Deukmejian, a fund-raising appeal and an absentee ballot application.

The voter could fill out the application and send it right back to GOP headquarters in a postage-paid envelope.

Republican Party workers sorted the 100,000 completed applications into 58 groups, one for each county. They mailed or hand-delivered them to the appropriate county registrars, who then sent the ballots to the voters.

Democrats made the process much easier for the Republicans by passing a law in 1978 removing the requirement for an absentee ballot of a letter stating why the voter could not appear at his precinct polling station.

Many states, including Maryland and Virginia, still require voters to give a reason for requesting an absentee ballot. But some political organizers think this may not be an insurmountable handicap.

Virginia Republicans tried to mount a hasty absentee ballot campaign in a special state senate election in Newport News late last year, which Democrat Robert Scott narrowly won.

Clayton Roberts, the Virginia Republican Party's communications director, said a statewide absentee ballot campaign "is something we are going to be looking at."

Audrey Piatt, elections and registration coordinator for the Virginia Board of Elections, said either party could make copies of the official state absentee application and send it to voters, as was done in California.

A few states still require absentee ballot applicants to have their signatures notarized, Lewis said.

Such restrictions would effectively bar a mass absentee ballot campaign, but political organizers feel that the laws in many states with large populations are still conducive to effective ballot-by-mail efforts.