The debate on Thursday night between Vice President Joseph R. Biden Jr. and Representative Paul D. Ryan will be split into nine, 10-minute segments, with Martha Raddatz, the moderator, choosing the topics for each.
Ms. Raddatz, the senior foreign affairs correspondent for ABC News, has said she plans to alternate between domestic and foreign policy during the 90-minute debate. Her success at keeping to that schedule may depend on how feisty the two candidates are.
But if she sticks to her plan, the debate could become a rare, broad-ranging discussion that offers voters a good opportunity to judge the two men and their capabilities.
While it is hard to know exactly what topics might come up , here is a look at some of the possible lines of questioning and the challenges they could pose for the candidates, on both substance and style.
1. JOBS, UNEMPLOYMENT AND THE ECONOMY
Substance: As the self-described “sheriff†of the 2009 stimulus law backed by President Obama, Mr. Biden's challenge will be to defend the much-maligned government program against Republican charges that it did not do enough to address high unemployment and economic stagnation. Mr. Ryan's task became harder after Friday, when the unemployment rate dropped to 7.8 percent, robbing him of the chance to hit the vice president on the administration's claim that stimulus spending would keep unemployment below 8 percent.
Style: Tone is especially important when talking about jobs and the economy. Being too glib about the challenges that people face could get Mr. Biden into trouble. But so can being to grim, as the vice president discovered at a rece nt rally, when he said the middle class has been “buried†for four years. Mr. Ryan needs to convey empathy - a trait that Mr. Romney's ticket is only now getting credit for having.
2. LIBYA AND TERRORISM
Substance: The Libya hearings on Capitol Hill on Wednesday provided the perfect opening for Mr. Ryan to hammer the Obama administration on the security before the raid in Benghazi and how their story changed after the raid. Mr. Biden will have to find a way to downplay the specifics even as he defends the administration's broader policy in the region. He could also have to explain why the administration took so long to characterize the attack as an act of terrorism.
Style: A discussion about terrorism may provide one of those signature moments that Mr. Ryan has to worry about. If he's not careful, he could give his rival a softball and Mr. Biden will slam it home, perhaps with his favorite line: “Bin Laden is dead and General Motors is alive.â€
3. MEDICARE AND THE RYAN BUDGET
Substance: There is little doubt that Mr. Biden will be on the attack here, trying to pin down Mr. Ryan on the particulars of his one-time plan to change Medicare into a voucher system. More broadly, the vice president will try to link Mr. Romney to Mr. Ryan's proposals.
Style: The challenge for Mr. Ryan will be twofold: avoid getting caught up in the intricacies of Congressional budgeting and don't come across as overly defensive. Both may be difficult for the Republican House Budget committee chairman, who is steeped in arcana and hemmed in by the constraints of having to follow the lead of his running mate.
4. IRAN AND NUCLEAR WEAPONS
Substance: Mr. Ryan's running mate has been highly critical of Mr. Obama's Iran policy, accusing him of not doing enough to prevent Iran from obtaining a nuclear weapon. But Mr. Biden, who has a lengthy record on foreign policy, is likely to push back, both by citing the intense sancti ons regime imposed by the United States and by pointing out the similarities between Mr. Romney's stated policy and the one the White House is pursuing.
Style: This is one of the areas that Mr. Biden might exploit in the hopes of taking advantage of the difference in experience between himself and Mr. Ryan, who has limited experience abroad, and needs to make sure voters can envision him as commander in chief, should that need arise.
5. TAXES, DEFICITS AND THE FISCAL CLIFF
Substance: With a serious fiscal crisis looming just after the election, both men will be eager to engage on this one. Mr. Biden is sure to go after the Romney-Ryan plan to cut taxes, while Mr. Ryan is likely to focus on the looming deficits - a key strength for the Republican ticket. Both will likely struggle to answer how the country can avoid falling off the “fiscal cliff†at the end of the year.
Style: Another danger zone for the wonky Mr. Ryan, who can descend into budgetes e if he's not careful. But Mr. Biden is a creature of the Senate and it's often fruitless negotiating sessions. He has to remember that he's speaking to the voters, not to his former colleagues in the Senate.
6. SYRIA AND THE ARAB SPRING
Substance: Syria presents another opportunity for Mr. Ryan to raise questions about the president's foreign policy choices, especially his handling of the unpredictable changes sweeping across Arab countries. Mr. Biden is likely to try and demonstrate that the administration grasps the complexities of the region in a way that Mr. Ryan and Mr. Romney do not.
Style: Diplomacy is an art, not a science, and Mr. Biden has to be careful not to seem like he's dodging the tough issues even as he's careful about what he says. For Mr. Ryan, the danger is in overreaching in criticizing the administration's policy, which could make him seem unsophisticated.
7. ABORTION AND CONTRACEPTION
Substance: The topic might have been passed over if not for Mr. Romney's comment this week that abortion legislation wouldn't be part of his agenda. That gives Mr. Biden an opening to press the administration's case against the Republican ticket on issues of particular concern to women. He will likely push on the cost and availability of contraception as well, noting Mr. Ryan's votes on the issues. Mr. Ryan will try to turn the contraception issue into a question of freedom for religious institutions.
Style: This is a tricky one for Mr. Ryan because the Republican ticket is trying to reach out to moderate, independent voters in the final 26 days. But he can't alienate conservative voters either, by seeming to run away from the Republican record on the issue. Mr. Biden will likely cite Mr. Ryan's votes on abortion and contraception in the hopes of setting that trap.
8. AFGHANISTAN, IRAQ AND DEFENSE CUTS
Substance: Mr. Ryan will be eager to lay blame for the looming defense cuts at the administr ation's feet in what could be a debate over the proper size of the military in a world dominated by terrorism concerns. Mr. Biden, who handled the withdrawal from Iraq for the president during the past four years, will tout the country's departure from a long war. Both will likely signal an eagerness to do the same in Afghanistan.
Style: Mr. Biden's age and experience means he may already have passed the commander-in-chief test. But Mr. Ryan needs to demonstrate to voters that they can envision him directing troop movements if he should become president. Talking smartly about the country's wars and the military budget is an opportunity to do that.
9. IMMIGRATION
Substance: Mr. Romney recently said he would not seek to deport young immigrants who signed up under a temporary Obama program. Mr. Biden is likely to seize on that comment as an example of Mr. Romney's differing position on immigration. Mr. Ryan may push the vice president on efforts to secure the border, and could bring up the controversial gunrunning effort called Fast and Furious, which Republicans in Congress have been investigating.
Style: Hispanics are a huge voting block that will influence the election's outcome. So far, Mr. Obama is winning big among the voting group, in part because of the perception that Republicans will take a harder line against illegal immigrants. A softer tone by Mr. Ryan could help the Republican ticket peel off some of those voters in states like Arizona, Colorado and Florida.
Follow Michael D. Shear on Twitter at @shearm.
