To paraphrase Defense Secretary Donald Rumsfeld, you don't go to vote with the candidates you want -- you go to vote with the candidates you have. Meaning, sometimes the names on the ballot fall short of the ideal.

That's the Democratic primary for lieutenant governor in a nutshell, but it shouldn't discourage voters from making a careful choice May 16. After all, whoever the party nominates could someday be called on to step in for or replace the governor, as happened in the previous two administrations.

One thing is clear. Pennsylvania's second-in-command should not be Lt. Gov. Catherine Baker Knoll. The former state treasurer from McKees Rocks, who won nomination four years ago as the only woman in a nine-candidate field, has been making headlines for all the wrong reasons.

She has shown confusion and befuddlement while presiding over the Senate, a key function of her job. She has become known for malaprops and misstatements, including reference to Gov. Ed Rendell as "Edward G. Robinson." She turned up in July at the funeral in Carnegie of a soldier killed in Iraq, handed out a business card, appeared to be campaigning and made a remark that was interpreted as criticism of U.S. military action.

This spring, with three challengers in the Democratic primary, Ms. Knoll, 75, has been kept under wraps by her campaign. She has refused to debate her opponents, and she declined to be interviewed by the Post-Gazette editorial board, with her spokeswoman saying the schedule was full.

Uh-huh.

Pennsylvania would be better served if gubernatorial candidates could choose their own running mates, as presidential nominees do. But the state lets primary voters forge the executive ticket, sometimes with hair-raising results. This year the incumbent lieutenant could hurt, not help, the chances of Ed Rendell -- unless Democratic voters intervene.

Two challengers are Gene Stilp of Dauphin County and William Hall III of Northampton County, both 55.

Mr. Stilp, a consultant, is the anti-pay raise crusader who has filed lawsuits and held marches to challenge the political status quo in Harrisburg. Although we agree with some of his positions, he is more interested in using the office as a platform than in carrying out its function. He contends, almost simultaneously, that anyone can do the job and that this is a job too important to be left to anyone. The activist also did not satisfy us with his non-answer on what he would do while presiding over a Senate that might take an action that is at odds with his views.

Mr. Hall is a retired builder who got the political bug from watching Ross Perot run for president. He believes Gov. Rendell has been good for Pennsylvania and would support his agenda, along with certain reforms like a lobbyist disclosure law. He also wants to secure funding for Medicaid and figure out a way to deliver more relief on property taxes. To pursue that agenda, he should be running for a seat in the Legislature, not lieutenant governor.

That leaves Valerie McDonald Roberts, 50, of Churchill. The Allegheny County recorder of deeds is an energetic and articulate public servant well-known in Western Pennsylvania. She spent five years on the city school board, seven years on City Council and is in her fifth year with the county. She's had private-sector experience, too, as a chemist for Gulf Oil Corp. and USX Engineers and Consultants Inc. She earned her bachelor's and master's degrees at the University of Pittsburgh, both summa cum laude.

Last June we cavalierly dismissed her notion to run for lieutenant governor and recommended that she consider another office closer to home. What a difference a year makes.

In this field, in this primary, she is the standout candidate. She would be a fiery, intelligent teammate for Ed Rendell (and not just because she's an African American and he'll be facing an African-American opponent). She is not running so much against the incumbent as she is running for the office -- something the incumbent this spring has chosen not to do.

In the aftermath of the pay-raise debacle, elected officials cannot take their office for granted. Now more than ever, candidates must present themselves to the public, interview for the job with the people. Catherine Baker Knoll hasn't done that. Valerie McDonald Roberts has -- and that's why she's earned the Post-Gazette endorsement.