Hillary Clinton, buffeted by an insurgent Bernie Sanders and durable doubts about her honesty, helped her campaign and the causes she's long advocated with a solid debate performance Tuesday night. She was sharp on the issues but also took some of the edge off her often-brittle campaign style. But despite the applause from the friendly audience and collegial approach of her Democratic opponents, voters will have more questions and deserve more answers from the party's front-runner.

Politically, Clinton may be relieved by Sanders' gracious dismissal of an e-mail scandal even she admits was a mistake. But many voters — not to mention congressional committees and possibly the FBI — may not be satisfied.

"I have been as transparent as I know to be," Clinton claimed. That may be the problem, given the ethical issues that have dogged her campaign and career.

On policy, Clinton focused on some of the key issues most important to voters, including income inequality, immigration reform and gun control. But she was less expressive about health care and even foreign policy, which should both be expertise areas for the former secretary of state. She also seemed tone-deaf on the deep diplomatic implications of rejecting a Pacific free trade pact designed in part as a counterbalance to China's rise. Clinton's cynical flip-flop on an agreement she advocated as America's top envoy may be in response to Sanders, who has been consistent — but wrong — about free trade.

As for Sanders, his decision not to rehearse for the debate showed in style, but not in substance. His positions and passion have energized the election, and he's been disciplined in focusing on issues in lieu of personal attacks. But his unwillingness to embrace capitalism suggests his appeal is limited. Indeed, "we are not Denmark," as Clinton reminded Sanders on Tuesday, and for the Democrats to win they need a candidate more palatable to moderate Democrats and independents.

After the debate, there's no doubt the field would be strengthened by a candidate like Joe Biden, whose extensive public service record and compelling personal story would give Clinton her most formidable opposition. Biden would likely offer a better defense on free trade, among other Obama administration priorities. And his deep relationships — and even respect — among some Republicans might help break the gridlock in Washington.

Clinton's leftward lurch is in part a response to Sanders' push for universal health care, Social Security expansion and free public college tuition, among other expensive ideas. Neither offered a convincing plan on how to pay for their plans without adding to the growing national debt.

As for Martin O'Malley, Lincoln Chafee and Jim Webb, each is unlikely to build beyond single-digit support. Each, however, is an admirable public servant, and O'Malley deserves credit for calling out DNC Chair Debbie Wasserman Schultz for limiting the number of debates. Because it's not only the party and the candidates who benefit from unfiltered exposure, but most important, the American people.