SACRAMENTO -- Gov. Arnold Schwarzenegger's campaign said Saturday it was withdrawing a TV ad that featured the governor appealing to voters to support his slate of ballot initiatives.

The move to drop Schwarzenegger from the airwaves comes at a critical time -- just 17 days before the Nov. 8 election.

His campaign dismissed the notion the ad -- the only one featuring the governor -- was pulled because of Schwarzenegger's falling approval ratings. Instead, they said TV ads are being rotated as part of a plan to educate voters about specific ballot measures.

Still, some observers said Schwarzenegger's ability to sell his ballot agenda might be limited because polls show he has the approval of only about 35 percent of voters.

"An overwhelming majority of voters think this special election is unnecessary and an overwhelming number of voters say they will not vote for Schwarzenegger again. Let's face it, he's unpopular," said Larry Gerston, a political scientist from San Jose State University.

Todd Harris, spokesman for Schwarzenegger's California Recovery Team, said there is no effort to hide the governor and pointed to his Saturday campaign stops in Southern California and a live TV forum planned for Monday.

"We've reached a stage in this campaign where the most important thing we can do is focus on the initiatives themselves," he said. "It is the initiatives that will be voted on Nov. 8 and we need to make sure the public understands how critical these four measures are in reforming California."

Harris said the ad does not address details of the governor's measures, while three others do. He said Schwarzenegger will be back in TV ads before Election Day.

The 30-second ad featuring the governor had been running for about a month. In it, Schwarzenegger speaks directly to the camera about the influence big labor unions have on the state and the need to pass his reform package.

"My goal as governor is to rebuild California -- rebuild our economy, our roads, our health care system and our schools," Schwarzenegger says in the ad. "But a broken system in Sacramento stands in the way, a system rigged to benefit big government labor unions who will do anything to preserve the status quo."

Other ads from the governor's team use actors talking about Schwarzenegger's initiatives and why they should be passed.

The Republican governor is pushing four measures that would impose a new state spending cap, redraw legislative districts, create a longer probationary period for teachers and restrict the use of union dues for political purposes.

Recent polls show only his teacher tenure measure and the union dues initiative are favored by voters.

Raphael Sonenshein, a professor of political science at California State University, Fullerton, said even if the campaign dropped the ad as part of a plan, the fact that he is vanishing from the air is telling.

"If the election had been going according to plan, the only ad they would be running would have Schwarzenegger in it," he said. "It's hard not to be skeptical of their reasoning especially since they have been saying for months that private polls show him and his initiatives in a much more positive light."

Meanwhile, hundreds of teachers knocked on doors in the Los Angeles area to remind voters to get to the polls next month. The California Teachers Association opposes the governor's proposal to extend the probationary period for teachers.

"We're working on people who we think will vote no and need a reminder," said union president Barbara Kerr. "We don't want them to stay home."