SACRAMENTO—The race for secretary of state this fall could be the Republicans’ best hope of retaining a statewide office, and it has left the Democratic challenger struggling to find a weakness she can exploit in her moderate opponent.

Incumbent Secretary of State Bruce McPherson has steered a centrist course since being appointed by Gov. Arnold Schwarzenegger in March 2005 after Democrat Kevin Shelley resigned amid allegations of financial impropriety.

That has helped him win over many Democrats and left-leaning organizations. He has received the endorsement of groups such as the California Teachers Association, an influential player in statewide political campaigns. He is the first Republican the group has supported for statewide office.

A McPherson win would boost the spirits of his fellow Republicans, who haven’t seen significant victories in California statewide races since 1994.

Such an outcome also could have implications for McPherson beyond the next term, said Mark Baldassare, director of research for the Public Policy Institute of California.

“If McPherson wins, he will join a very select group of Republicans that have been elected to statewide office this decade,” he said. “Instantly, this distinct status will make him a leading candidate for statewide races such as governor in 2010.”

But Democratic state Sen. Debra Bowen, D-Marina del Ray, could pull ahead if California’s decidedly left-leaning voters stick to party lines.

“Any Republican candidate, including McPherson, faces the difficult challenge of overcoming the Democratic edge in voter registration in the California electorate,” Baldassare said.

Bowen has made a name for herself as a champion of privacy rights and an outspoken critic of the current state voting system under McPherson, who has made voting reform _ namely electronic voting _ the centerpiece of his term.

The road toward e-ballots has been bumpy at times, and many Californians have expressed concerns after a string of glitches in recent years. Those included the revelation in May that a feature on the widely used Diebold Election Systems computerized machines could allow someone to upload unauthorized software.

Bowen hopes to capitalize on suspicions of the machines as voters use them to cast their ballots.

“We have a little crisis of confidence in our voting systems here in California,” she said, noting that the absence of paper records from touch-screen voting makes her uneasy.

As chairwoman of the Senate elections committee, she has been active in voting issues and this year sponsored a successful bill requiring all electronic voting machines in the state to produce a paper trail that will be retained by election officials for 22 months after the election.

The bill was signed into law in August and will take effect Jan. 1.

McPherson says he, too, has been a longtime supporter of paper verification. He maintains that California’s voting system has seen vast improvements since he took office.

“This is the biggest change in the voting process in the history of the nation, and we’re ahead of other states,” he said of the transition from paper to electronic ballots.

In addition to overseeing the 2005 special election, McPherson’s efforts include the creation of the Office of Voting System Technology Assessment, a technology and testing unit that all new systems must pass before they are approved.

He also set up a statewide voter database to help prevent voter fraud.

Although their methods differ, both Bowen and McPherson use the same language to describe their goals for voting reform _ reliability, transparency and accessibility.

That will be a tall order for whoever wins in November, said Kim Alexander, president of the Davis-based California Voter Foundation, a nonprofit group that advances electronic-voting reforms.

“Carrying out that responsibility is increasingly challenging because of competing pressures by groups who want more accuracy and more security and by election officials at the local level who are often reluctant to increase their workload,” she said.

A longtime privacy advocate, Bowen’s other campaign priorities include adding sexual assault victims to the state’s Safe at Home program, which allows abortion clinic workers and victims of domestic violence to keep their addresses confidential and vote by mail.

Both candidates said they would try to engage young voters and further campaign finance reform.

Meanwhile, McPherson and Bowen are trying to persuade undecided voters and drum up enthusiasm for an office that often fails to capture broad public interest.

McPherson enjoys an advantage with heavily stocked campaign coffers. At the end of July, he had $708,000 in remaining funds, compared to Bowen’s $180,000, according to Cal-Access, the state’s online database of candidates’ financial information.