Why watch the vice-presidential debate? Entertainment value.

The vice-presidential debate Thursday might not change much in the polls, but it should provide more zingers than the first presidential debate did – and be a warm-up for Obama-Romney Round 2.

Did last Wednesday's presidential debate not have enough fireworks or personal attacks for you? Were you bothered, as some Democrats have been, that President Obama didn't call out Mitt Romney on some of his misleading claims (or vice versa)?

Tune in Thursday night, then, when Vice President Joe Biden faces off against GOP vice-presidential candidate Paul Ryan, and sparks are almost certain to fly.

Given the "attack dog" role that most VP candidates assume, it's not surprising that vice-presidential debates are often heavy on aggression, and contain some memorable one-liners. (Think Lloyd Bentsen telling Dan Quayle in 1988, "Senator, you're no Jack Kennedy," or Walter Mondale telling Bob Dole in 1976 that he "has richly earned his reputation as a hatchet man.")

Beyond the entertainment value, of course, they may not mean much. In 2008, a record number of viewers tuned in to watch Sarah Palin debate Mr. Biden, wondering, primarily, whether then-Governor Palin would be in over her head.

Palin's "Can I call you Joe?" intro line was richly parodied afterward – and Tina Fey was surely thanking her for it – but in the end, Palin put in a credible performance and Biden reined in his attacks to avoid appearing like a bully, and the debate had zero effect on the polls.

That's likely to be the case again this time, although Democrats are certainly hoping that Biden can lay the groundwork for Mr. Obama to recover from his poor first debate performance – which did, in fact, seem to have made a big difference in the polls, contrary to what most pundits expected beforehand.

For starters, expect Biden to be much more prepared – and willing – to call out Congressman Ryan on any claims he takes issue with.

The debate will cover both domestic and foreign-policy issues. Look for Medicare to loom large in domestic issues; it was a centerpiece of Ryan's budget proposal, and Mr. Romney's proposal to partly privatize Medicare was based largely on Ryan's ideas. It's also a key area where Obama's team is trying to stoke fears about what the plan will mean for seniors' expenses down the road.

Given Biden's extensive foreign-policy experience, international issues should also make up a good chunk of the debate – and some viewers may be interested to see how Ryan, who has far less exposure on foreign policy, measures up.

In the end, the debate may be much more entertaining than the somewhat dry presidential debate from last week, which seemed heavier on dense numbers and dry explanation rather than zingers and one-liners.

But if you're looking for an event that could have a measurable effect on the race, you may need to wait until the following Tuesday, when Obama and Romney face off for a second time, this time taking questions from undecided voters in a town-hall-style event.