(CNN) - Democrats tried to heal the wounds of a long primary season Tuesday with a primetime call for unity from the party's one-time presidential frontrunner, Hillary Clinton. They also repeatedly tied John McCain to an unpopular George W. Bush and a faltering economy.
On Wednesday, the 45th Democratic National Convention turns its attention to a potential weak spot for Barack Obama: foreign policy. It also officially nominates its presidential ticket and yields the podium both to former President Bill Clinton and presumptive vice presidential nominee Joe Biden.
The lineup of speakers for day three of the convention -- which has been tagged with the theme of "Securing America's Future" -- features a roster of Democratic foreign policy and national security heavyweights.
The list includes, among others: former Secretary of State Madeleine Albright; Senate Armed Services Committee members Evan Bayh and Jack Reed; former U.N. Ambassador Bill Richardson; retired Army Lt. General Claudia Kennedy; and Iraq war veteran Tammy Duckworth. Texas Rep. Chet Edwards, the only House member to be seriously vetted as a potential running mate by the Obama campaign, is expected to discuss veterans' issues.
Also addressing the convention: Senate Foreign Relations Committee member -- and 2004 Democratic presidential nominee -- John Kerry.
Obama's apparent weakness on issues related to foreign policy and national security has been a matter of increasing concern to Democratic strategists. Russia's conflict with the neighboring Republic of Georgia has highlighted the question of the candidates' fitness to be commander in chief.
According to an August 23-24 CNN/Opinion Research Corp. poll, 78 percent of registered voters believe McCain can handle the responsibilities of commander in chief. In contrast, only 58 percent believe Obama can handle those responsibilities.
The CNN poll also found that 60 percent of voters say they believe McCain would better handle the issue of terrorism, whereas only 36 percent have more faith in Obama. A clear majority of voters says it believes McCain is more likely than Obama to be a strong and decisive leader.
McCain is trying to blunt any momentum the Democrats can generate from their convention in part by pressing his advantage on national security issues. His campaign released a new ad Tuesday raising the specter of several potential national security crises. It then shows a clip of Hillary Clinton during the primaries arguing that she knows "Sen. McCain has a lifetime of experience that he will bring to the White House. And, Sen. Obama has a speech he gave in 2002."
Obama's best response to questions about his preparedness on foreign policy and national security may be his selection of Senate Foreign Relations Committee Chairman Joe Biden as his running mate. Delaware's senior senator is expected to be nominated for vice president by acclamation, followed by a 20-minute acceptance speech at the close of the evening.
Finally, Wednesday will also witness a continuation of the drama surrounding the Clintons and their role in Barack Obama's Democratic Party.
Former President Clinton is expected to speak before the convention shortly after 9 p.m. ET. Sources told CNN earlier this week that the former president was unhappy with his assigned speech topic for the convention, national security. He reportedly would have preferred to discuss the economy -- the issue that, more than anything else, helped propel him to the White House 16 years ago.
Controversy also surrounds the role of Hillary Clinton's nearly 1,700 pledged delegates. It is believed that Clinton has reached an agreement with the Obama campaign to allow some delegates to cast votes for her before a motion is offered to cut the roll call short and nominate Obama by acclamation. It remains to be seen, however, whether some Clinton delegates will try to start a roll call floor demonstration that may prove embarrassing to convention organizers.
While Clinton has strongly urged her supporters to support Obama, evidence shows a growing number of her supporters are instead choosing to support McCain. A CNN poll taken at the end of June indicated that 16 percent of Clinton's Democratic supporters intended to vote for McCain.
The August 23-24 CNN poll showed that 27 percent of her voters supported the Arizona senator.