Californians are left with a deeply unsatisfying choice for the U.S. Senate this year. The incumbent, Democrat Barbara Boxer, has failed to distinguish herself during her 18 years in office. There is no reason to believe that another six-year term would bring anything but more of the same uninspired representation. The challenger, Republican Carly Fiorina, has campaigned with a vigor and directness that suggests she could be effective in Washington - but for an agenda that would undermine this nation's need to move forward on addressing serious issues such as climate change, health care and immigration.

It is extremely rare that this editorial page would offer no recommendation on any race, particularly one of this importance. This is one necessary exception.

Boxer, first elected in 1992, would not rate on anyone's list of most influential senators. Her most famous moments on Capitol Hill have not been ones of legislative accomplishment, but of delivering partisan shots. Although she is chair of the Environment and Public Works Committee, it is telling that leadership on the most pressing issue before it - climate change - was shifted to Sen. John Kerry, D-Mass., because the bill had become so polarized under her wing.

For some Californians, Boxer's reliably liberal voting record may be reason enough to give her another six years in office. But we believe Californians deserve more than a usually correct vote on issues they care about. They deserve a senator who is accessible, effective and willing and able to reach across party lines to achieve progress on the great issues of our times. Boxer falls short on those counts.

Boxer's campaign, playing to resentment over Fiorina's wealth, is not only an example of the personalized pettiness that has infected too much of modern politics, it is also a clear sign of desperation.

In past elections, Boxer has had the good fortune of having Republican opponents who were inept, underfunded, on the fringe right - or combinations thereof. Her opponent this time, Fiorina, is proving to be articulate, well-funded and formidable.

Unfortunately for Californians who are eager for change, Fiorina has firmly staked out positions that are outside of the state's mainstream values and even its economic interest. The list only begins with her openness to offshore oil drilling, her opposition to the Roe vs. Wade abortion rights ruling and her unwillingness to support even the most commonsense gun-control measures to keep assault weapons off the street or to deny guns to suspected terrorists on the federal "no fly list."

One might argue, as Fiorina does, that the latter are settled issues and thus should not be determinant in an election that should be laser-focused on jobs. But efforts to expand health care and take action against climate change - issues with both moral and economic consequences for future generations - are very much in play, especially if Republicans gain control of the Senate. Fiorina has said she would vote to repeal the landmark health care bill, and her support for a state initiative that would halt definitive action on climate change until unemployment reaches 5.5 percent shows a disdain for science and a disregard for this state's potential to take the lead in an emerging green economy. She is similarly unrealistic in her insistence that immigration reform must wait until the U.S.-Mexico border is absolutely secure.

It is a dismal choice between an ineffective advocate for causes we generally support and a potentially strong advocate for positions we oppose. Neither merits our endorsement for the U.S. Senate.