The presidential battle for California has become a tossup, with only 10 percent of the voters remaining undecided, according to a new poll.

Democrat Michael Dukakis has 44 percent and Republican George Bush 43 percent, according to a survey of 1,360 registered voters polled Wednesday through Saturday. The poll, taken by the San Francisco Examiner and San Francisco's NewsCenter 4, has a margin of error of plus or minus 2.7 percentage points."Dukakis appears to have held onto the vote he had in June," said Examiner pollster Stephen Teichner. "But there's been no great movement for him since then. Bush appears to have picked up a little, to the point where the race is absolutely a tossup."

The results support recent national polls indicating Dukakis has lost the 15- to 17-point advantage he enjoyed after the Democratic convention in July. A Field Poll showed Dukakis ahead in California last month by 16 points.

But California, the biggest single prize with its 47 electoral votes, has not followed the national trend for the low undecided total.

"For all practical purposes, that eliminated Bush's ability to ride a post-convention bump in his favor," he said. "For Dukakis, however, it may mean he now will have to push earlier than he'd planned to focus on undecided voters."

As the challenger to an incumbent administration, Dukakis has the special burden of appealing for change before voters tune out the candidates.

In 1984, Teichner said, polls showed majorities agreeing with Democratic contender Walter Mondale on issues but favoring President Reagan by landslide proportions anyway. "They stopped thinking about the race," Teichner said.

However, Bush remains far behind Reagan's 1984 support in the polls at this stage. In particular, the survey suggests that Bush lacks the strong backing of conservative Democrats who voted for Reagan last time. That group, the so-called "Reagan Democrats," favors Bush by only three points, 44 to 41 percent.

Voters who consider drugs to be the main issue support Bush, 50 to 39 percent, while those who consider the federal budget deficit to be the No. 1 problem favor Dukakis, 50 to 43 percent.

White voters surveyed supported Bush, 47 to 41 percent; blacks backed Dukakis, 79 to 11 percent; and Latinos favored Dukakis by 61 to 31 percent.

Women now favor Dukakis by 46 to 40 percent. In an Examiner exit poll taken after the June primary, he enjoyed a 52 to 28 percent lead among women, with an overall advantage of 46 to 37 percent.