If you noticed your mailbox was stuffed yesterday with negative political ads and the TV commercials about your favorite candidates were particular nasty, here's the reason:

"Election Day starts Monday," said Sarah Pompei, spokeswoman for Meg Whitman, the front-running GOP candidate for governor.

Starts is the key word here. While the finish line for the heated primary election is June 8, the day the polls open, a sizable percentage of the state's voters will get their ballots in the mail this week.

It's part of an extraordinary trend that has forever altered the way California's political campaigns are run.

"We've gone from an election day to an election month," said Allan Hoffenblum, a former Republican consultant who handicaps election campaigns as publisher of the nonpartisan California Target Book.

The trend's roots date to 1978, when the state loosened the rules that said "absentee ballots" could be cast only by people who were going to be traveling on Election Day or who had medical problems that would keep them from the polls. But the number of mail voters began soaring in 2002, when Californians were allowed to register as "permanent absentees" rather than request a mail ballot each election.

That's made things a lot more complicated for campaign strategists. In a way, they're running two races — one aimed at reaching voters before Election Day and another aimed at the often-hard-to-time "rolling election" of the vote-by-mail crowd.

Hoffenblum, 69, remembers the days when "absentee ballots" were so rare that campaigns used to send volunteers down to election offices to find out who had applied for them. The runners would copy down names and addresses, write the information in long hand on a mailer, slap a stamp on it and drop it in a mailbox.

Today, campaigns get the list of permanent vote-by-mail voters on a CD and let laser printers do the work. And winning over those who vote by mail has become a key part of winning elections — not an afterthought.

"In the past, campaigns could wait until the last few weeks before an election to contact voters," said Jude Barry, a San Jose political strategist. "Now it's over six to 12 weeks. So you really have to stretch your dollars over a longer period of time. And that becomes a real challenge to spend it wisely."

Absentee turnout played a vital role in San Jose Councilwoman Madison Nguyen's defense against a recall effort in March 2009. More than 82 percent of the 13,000 ballots were cast early — a dramatically high share that Nguyen's supporters worked hard to encourage by signing up sympathetic voters.

Because of that push, the outcome was practically decided "the weekend before absentee ballots went out," said Melanie Jimenez, Nguyen's campaign manager.

The early-voting trend might prove critical in the GOP primary in which Whitman, the former eBay CEO, and state Insurance Commissioner Steve Poizner are vying for the right to face Democratic Attorney General Jerry Brown in the fall.

Although Poizner has recently cut into Whitman's once-commanding lead, he needs to make up ground quickly because early voters are expected to lean heavily for Whitman, assuming recent polls are true. So even if Poizner is slightly ahead of Whitman in ballots cast on Election Day, he could lose.

In recent days, the Whitman campaign began targeting seniors — who tend to mail in their ballots earlier than younger voters — with an ad saying Poizner wanted to hurt retirees by changing Proposition 13.

The surge in early voting also has changed business as usual for the pollsters who labor to handicap voters' attitudes.

In some ways, it makes the job easier, said Mark DiCamillo, director of the nonpartisan Field Poll. Anyone who replies they've already voted — as many as one in four respondents in the final poll before Election Day — "becomes, by definition, a likely voter," he said. DiCamillo said that's one of the reasons the past decade has been the Field Poll's most accurate when it comes to final-week polls.

In essence, pollsters can now release meaningful "exit polls" days before the polls open. But DiCamillo, for one, has resisted that, saying: "We don't want to demoralize people."

Another election standby whose days may be numbered are nasty hit pieces that arrive in the mail just before Election Day, giving the besmirched candidate little time to respond. San Jose has had its share, including a piece from a committee backing Assembly candidate Manny Diaz that called his rival, Tony West, an "Oakland Raider." The line ostensibly aimed to paint West as a carpetbagger, but some believed it was meant to connect West, who is black, with a city that has a substantial black population. West lost in the heavily Latino district.

Some strategists suggest those pieces are bound to continue, because even if voters are holding absentee ballots, they don't always turn them in right away. They say the more complicated and contested the ballot, the longer it takes for voters to return them.

In the 2008 presidential election, for instance, just 12 percent of Santa Clara County's mail-in ballots had been returned three weeks before Election Day, according to the registrar's election division coordinator Elma Rosas. Two weeks out, that percentage climbed to 28 percent, and one week out it was 52 percent. By Election Day, 84 percent of the ballots were returned.

That 2008 election also set a watermark for the number of mail ballots cast: 41.6 percent of the state's total. Campaign officials say they won't be surprised if 60 percent of the ballots cast in the June 8 primary are mail-ins.

One big reason: Local governments are in dire fiscal straits, and politicians are looking for ways to trim election costs.

"We're definitely moving to all-mail ballots,'' said Barry, the San Jose strategist. He notes that in Oregon, it's been all-mail ballots all the time for more than a decade, "and they have a 70 percent participation rate."

In California, sparsely populated Sierra and Alpine counties already have all-mail voting. So do 38 of 39 counties in Washington state.

Bill Lunch, chairman of the Political Science Department at Oregon State University, said he was originally dead-set against all-mail-in ballots before voters in his state overwhelmingly passed an initiative in 1998 requiring them for every election. But Lunch now acknowledges that all-mail voting has proved enormously popular, in large part because it's so convenient.

All of which suits 90-year-old Patrick Aubry of San Jose just fine, even though his polling place is only a couple of blocks away.

"I've got arthritic knees and a temperamental car," said Aubry, a retired accountant. "I don't miss going to the polling place at all."

Contact Ken McLaughlin at kmclaughlin@mercurynews.com or 408-920-5552.

voting by mail
Here are some questions and answers about voting by mail.

Why do many election officials prefer that people vote by mail?
They say the cost of processing a mail-in ballot is roughly 30 percent less than one cast at the polls. "You don't have to hire and train from 1,500 to 2,000 poll workers or use staff time to recruit them," said David Tom, elections manager in San Mateo County.
How do the workers at the registrar's office know the right person is sending in the ballot?
The staff compares each voter's signature on the outside of the envelope with the signature on the voter's registration card. The process is made easier by new digital-scanning technology.
How are vote-by-mail ballots counted?
In general, they're counted the same way as the ballots cast at a polling place. The mail ballots can be opened seven business days before Election Day and run through an optical scanner, but the results aren't tabulated until the polls close on election night.
What if I change my mind after I mail in a ballot?
Sorry. As the song said: It's too late.
I heard Gov. Arnold Schwarzenegger vetoed a vote-by-mail bill last year. What was that about?
California Secretary of State Debra Bowen sponsored a bill that would have allowed people who vote by mail to find out whether their ballot was counted -- and if not, why not. The governor said he vetoed the bill because he didn't want counties to incur additional costs. But most election officials say computer technology makes it inexpensive, noting that many large counties such as Santa Clara already allow voters to check online to see whether their votes were counted.
When is the last day to apply for a mail-in ballot?
June 1. Applications are available on registrars' websites or at local election offices. There's also a form on the sample ballots that will be sent out this week.
Sources: California Secretary of State's Office, Santa Clara County Register of Voters.