It's over. The last of the Democratic primaries notable for the near-equality of their importance have been held, and Sen. Barack Obama secured enough delegates to claim the nomination. Some 32,000 people gathered Tuesday night in St. Paul, Minn., to hear Obama deliver a symphonic speech whose crescendo shook the convention center. For the first time in American history, a major political party will nominate an African-American for president.

Obama was toughened and smartened by his grueling battle with Sen. Hillary Clinton, who should now preserve her bright future in her party by working to help Obama win over the voters who preferred her to him.

Clinton's overwhelming victories in states like Pennsylvania and Ohio highlighted Obama's lack of appeal to white, working class voters. He appeals to them less not because of his race, but because he has yet to convince people who struggle to pay the bills and worry about losing their jobs that he understands their plight and knows how to help them.

Obama will have to prove that he has a sound economic policy, one that will put a foundation under his towering rhetoric. No issue, not even the needless war in Iraq, will overtake voters' fears that the economy is sinking and with it their children's future standard of living. The plans Obama puts forth will have to be concrete and make a convincing case that his administration will reverse the growing gap between the rich and everyone else.

While Obama can speak from experience on economic issues, that's not the case with foreign policy or military affairs. This will be a clear contrast to his Republican opponent, Vietnam hero John McCain.

Obama will have to convince voters that he won't, as his opponents claim, have tea with radical Iranian President Mahmoud Ahmadinejad on Day One, but be a pragmatic and tough negotiator willing to use force when necessary. Naming the foreign policy experts who will advise him and possibly serve in his cabinet would give voters an idea of who he would listen to and what kind of policies he would pursue. The public will have to be persuaded that his plan to extract American forces from Iraq will not, as McCain charges, guarantee the need to sacrifice many more lives in a wider war that would follow Iraq's collapse.

Obama made history this week. If he is to do so again in November, voters will have to agree that his intelligence, honesty and sound judgment more than compensate for his relative inexperience.