With just three candidates left, the Democratic presidential race isn't nearly as contentious as the Republicans'. Polls indicate Democratic voters are lining up behind Hillary Clinton, who had a strong performance in the party's first debate in October and followed it up with an affirmative showing at the 11-hour Benghazi hearing.

That doesn't mean Clinton's two challengers, Sen. Bernie Sanders (I-Vt.) and former Maryland governor Martin O'Malley, are giving up. Expect them to challenge Clinton in the party's second debate, hosted Saturday night by CBS in Des Moines, Iowa. They will likely try to draw comparisons between their lengthy liberal records and Clinton's more-moderate stances from the last time she ran for president.

On matters of both politics and policy, the three candidates clearly have a lot to talk about. Here are the top 13 issues likely to be discussed at Saturday's Democratic debate:

1. Terrorism and the Islamic State

The tragic events in Paris on Friday night will surely be heavy on everyone's minds when the Democratic candidates take to the debate stage. And CBS has assured some of the questioning will focus on how to combat terrorism.

"Last night's attacks are a tragic example of the kind of challenges American presidents face in today's world and we intend to ask the candidates how they would confront the evolving threat of terrorism," CBS News vice president and Washington bureau chief Christopher Isham said in a statement.

The Islamic State has claimed responsibility for the Paris attacks, which French President Francois Hollande said amount to an act of war from the terrorist group. France is a U.S. ally in launching air strikes over Iraq and Syria to disrupt the terrorist group, which came to rise amid leadership vacuums in the Middle East in 2013 and 2014.

But the battle recently got more complicated with Russia's sudden intervention this fall in Syria to attempt to prop up Syrian President Bashar al-Assad. Not coincidentally, Obama announced he's putting 50 Special Ops commandos on the ground in Syria, appearing to go back on his past statements he wouldn't commit ground troops to Syria.

Republicans have tried to link Clinton's time as secretary of state to the rise of the Islamic State; Clinton has said the long-running civil war in Syria led to the terrorist group's outgrowth. She has advocated for "doing more to help the rebels" and instituting a no-fly zone in Syria, a notable departure from Obama and her main challenger, Sanders. Clinton has not said whether she would dedicate U.S. troops to creating the no-fly zone.

Whatever has been said before though, the events of Friday night certainly make the issue much more salient and could change things for everyone involved.

2. Hillary Clinton's past

It's not a new story, but on the campaign trail Thursday, Clinton brought up that time she allegedly tried to join the Marines but was rebuffed because she was too old.

Here's the answer to one of the most Googled questions about one of the most Googled candidates.

The story, which she first shared as first lady in 1994, immediately drew skepticism because it apparently happened in 1975, right as she was moving to Arkansas and marrying Bill Clinton. Washington Post Fact Checker Glenn Kessler revisited the details and gave her two Pinnocchios, meaning there were "significant omissions and/or exaggerations."

This re-airing could be perfectly timed for Clinton's rivals. Should they choose to go personal, questioning Clinton's honesty about her past could be a perfect "in" for them; polls consistently have shown that voters are worried about whether Clinton is honest or trustworthy. Look at this graphic, from August:

But they'll have to be careful just how hard they go after Clinton. A new Washington Post-ABC News poll find Democrats love Clinton, giving her significantly better favorability marks than Sanders.

3. Clinton's e-mails

The FBI is continuing its inquiry into whether and what classified information crossed the private e-mail server Clinton used almost exclusively while secretary of state. Politico reports the FBI is stepping up its inquiry into a potential "full-blown investigation," though the details are murky.

Still, Clinton had hoped to put the e-mail story behind her after a strong debate performance last time around, where she got a little help from Sanders, who emphatically declared "the American people are sick and tired of hearing about your damn e-mails."

That hasn't happened. As news about her e-mails refuses to fade -- the State Department is still releasing them in batches every month or so -- Sanders has clarified his debate outburst. He told The Wall Street Journal in a recent interview he believes the FBI should continue investigating Clinton's e-mails. "You get 12 seconds to say these things," he said by way of explanation.

More recently, though, Sanders again suggested this issue has been aired by the media too much.

How much he'll say about Clinton's e-mails at Saturday's debate is an open question.

4. Is Bernie Sanders a Democrat?

"I am a Democrat now," declared Sanders in a recent Sunday TV interview. But is he? He's the longest-serving independent in Congress, having been one for the quarter-century he's been in office.

Before this election, Sanders also vocally criticized the Democratic Party in books, speeches and interviews -- including suggesting in 2011 that President Obama could use a primary challenger.

Sanders faces the dual challenge of explaining to skeptical Americans why a socialist should be president and what his brand of socialism -- "democratic socialism" -- is. In the last debate, he sold the virtues of economic equality in Scandinavian countries like Denmark only to be shot down by Clinton, who said the United States "is not Denmark" and that she, too, supports more economic equality.

Sanders has tried to clarify ambiguity around his political ideology by giving a speech, but it doesn't help that a recent Gallup poll found half of Americans say they wouldn't consider voting for a socialist -- and that more would consider voting for a Muslim or atheist.

One bright spot for Sanders? A new New York Times-CBS News national poll shows 63 percent of Democratic primary voters thinks Sanders is "somewhat likely" to get his policies enacted as president, while 57 percent of voters think Clinton is "somewhat likely" to get things done.

5. Racial tensions

Racial tensions between communities and their police and university administrators are dominating national headlines and Democratic candidates' platforms. This time around, the nation's attention is on campus protests like those at the University of Missouri, where the university's president and chancellor stepped down Monday amid criticism they didn't do enough to address what some say is a pervasive culture of racism and bigotry on campus.

Democratic candidates realized earlier this summer that racial tensions would be a major focus for their campaigns. After either meeting with or being protested by members of the political movement Black Lives Matter, Clinton, Sanders and O'Malley have all put forth or beefed up plans to address racial disparities in America. Almost all the candidates agree with a recently unveiled bipartisan Senate criminal justice reform bill that would shorten the lengths of sentences for many non-violent drug offenders.

Interestingly, Clinton's and Sanders's supporters are sharply divided demographically, mostly between white and non-white. In South Carolina, for instance, an October CNN/ORC poll indicated Sanders led Clinton among white voters but trails Clinton by 55 points among African Americans. The picture is similar in a new Fox News poll:

6. Income inequality and Wall Street reform

In a time in which two-thirds of Americans (68 percent) believe our economic system favors the wealthy rather than being fair, according to a July Washington Post/ABC News poll, income inequality is arguably one of the top issues for Democrats in the race.

And they're mostly in agreement when it comes to the broad strokes, even as Clinton has weathered criticism that the former New York senator is too close to Wall Street. The candidates all agree that first, Wall Street executives who broke laws ahead of the 2008 recession should face criminal charges. Big banks should be broken up. Regulations like the 2010 Dodd-Frank financial reform law should be protected or even boosted.

But a Depression-era financial reform law repealed by President Bill Clinton, the Glass-Steagall Act, is a flashpoint between Clinton and her primary opponents. She said Oct. 6 she would not put her efforts into reinstating the law requiring big banks to separate their investment and commercial-banking practices -- even though a bipartisan coalition in Congress that includes Sen. Elizabeth Warren (D-Mass.) and Sen. John McCain (R-Ariz.) have proposed putting it back on the books.

Sanders and O'Malley have both said they'd reinstate Glass-Steagall as president, a statement that The Washington Post's David Weigel points out is akin to saying "then-President Clinton made a blunder that enabled the banker chicanery that led to the 2008 financial crisis."

7. Gun control

A summer and now fall filled with mass shootings -- including nine killed at a community college in rural Oregon on Oct. 1, two local Roanoke, Va., reporters gunned down in August on live television, a deadly Lafayette, La., movie theater shooting in July by a man with mental problems and another apparently racially motivated mass shooting at a black church in Charleston, S.C. -- has brought the gun debate back into the spotlight.

Nowhere is that more evident than on a Democratic debate stage. Gun control and how to stand up to the National Rifle Association dominated the party's first debate -- and proved to be a struggle for Sanders, as Clinton attacked him for a voting record she said looks more like and NRA supporter. (Sanders says he was representing his rural, Vermont community, which remains very pro-gun rights.) O'Malley has one of the strictest gun control platforms in the race: He wants to ban assault weapons and require that every person who buys a gun acquire a license and get fingerprinted.

Polls consistently show that upward of 90 percent of Americans support at least expanding background checks, but a majority of Americans are doubtful that changing gun laws will help prevent gun violence. In other words, it's complicated.

8. Veterans care

On the eve of Veterans Day, Clinton released a plan to expand health care for female and LGBT veterans and address a backlog of care in the Department of Veterans Affairs.

Her plan focuses specifically on improving access to child care and reproductive health care, since women are the fastest-growing population served by the embattled VA, her campaign said. She's also aiming to tailor services for LGBT vets, reports The Post's Anne Gearan.

Gearan reports O'Malley also released a plan to improve veterans health care on Monday, and Sanders has some suggestions for how to improve the agency on his Web site.

In the wake of last year's VA health care scandal, which called into question whether veterans whose lives were at stake were treated in a timely manner and how VA officials navigated around a backlog of claims, Republicans have suggested privatizing the agency. Clinton strongly opposes that idea.

9. Campaign finance reform

There are too many billionaires in politics: That statement is gospel among Democratic candidates like Clinton and Sanders and O'Malley, all of whom strongly opposed the 2010 Supreme Court Citizens United decision that opened up the spigots on campaign spending. Sanders doesn't even have a super PAC and Clinton has introduced a plan designed to weaken their influence on campaigns.

Lawrence Lessig, a Harvard professor, entered the Democratic race staking his candidacy on campaign finance reform, though he failed to meet CNN's polling requirements to appear in Democrats' first debate and dropped out of the race soon after.

10. Immigration reform

Unlike the 2012 campaign, there's no serious bid in Congress right now to reform our immigration system. Instead, Obama has twice acted unilaterally to extend deportation relief to about 5 million of the estimated 11 million immigrants in the country illegally.

But those executive actions have been held up in legal limbo thanks to a 26-state lawsuit questioning whether the president overstepped his constitutional bounds. On Monday, a federal appeals court sided with the states and upheld a lower court's injunction on the program.

Hillary Clinton called the court’s decision “wrong." The White House isn't giving up, though: The court's ruling against them actually gives Obama lawyers enough time to appeal to the Supreme Court, which could settle Obama's legacy on immigration once and for all.

The question for Democratic presidential hopefuls is how much farther they'd push Obama's executive actions. Clinton has been particularly out-front on that issue, a departure from her 2008 campaign. Back in May, Clinton promised immigration reform activists in Las Vegas she would work toward a pathway to citizenship and use executive action to stop even more deportations in the meantime, placing a priority on keeping families together.

Immigration could be an area where O'Malley, who is struggling to gain traction in the race, could make some noise. He recently took a trip to Nevada where he blasted Clinton's and Sanders's pre-2008 positions on immigration, which he argues were not as progressive as they are today.

11. College affordability

Debt-free college is another area of emphasis among most of the Democratic presidential candidates, thanks in no small part to the progressive wing of the party loudly making their voices heard on this issue. Sanders is the furthest to the left -- he wants to make public colleges and universities free, a plan that would cost an estimated $750 billion over 10 years and give the federal government wide control over those schools.

Clinton has her own $350 billion plan, paid for mostly by closing tax loopholes for the wealthy. It wouldn't make college free, but it would boost grants to schools to keep higher education costs low while allowing Americans with heavy federal student loan debt to refinance their loans.

12. Trade

In attempting to shepherd through not one but two major trade deals during his time in office, President Obama stands alone among most of today's Democrats. Liberal candidates like Sanders and O'Malley long ago came out against trade deals like the 12-Pacific-nation Trans-Pacific Partnership that negotiators recently finished up. They side with unions and some environmentalists who say the largest free trade agreement in a generation will ship American jobs overseas and promote evils like deforestation abroad.

Clinton has a much more complicated relationship with trade, something her opponents could hit her on if they want to. Her husband closed a major free trade deal with Canada and Mexico in the '90s. While secretary of state, Clinton helped negotiate and even praised the Trans-Pacific Partnership. But one week before the first Democratic debate, she announced she opposed the deal as it exists, saying that according to what she had seen, it doesn't go far enough to protect American workers' jobs.

Obama got authority this summer from Congress to negotiate the TPP, but he still has a politically difficult road to get Congress to officially okay it next year with an up-or-down vote.

13. Climate change and clean energy

As America continues to face extreme weather events that climate change activists say is evidence of the negative impacts of shifting weather patterns, Obama has invested heavily in alternative energy forms, such as solar and wind power.

Democratic presidential candidates almost all unilaterally agree the government needs to step in to help stop climate change and invest in more clean energy.

The litmus test among environmentalists has long been whether or not candidates would approve the fourth stage of the Keystone pipeline to ship Canadian oil to Nebraska, a politically touchy point for Clinton who recently said she opposes the pipeline but not before dithering for months.

Obama took that test off the table this month when he announced he won't approve the pipeline, setting the stage to also make major inroads on U.S. greenhouse gas emissions at a United Nations climate change summit in Paris at the end of November.

Clinton has now shifted her focus to trying to invest in coal communities hit by a shift to clean energy: On Thursday she unveiled a $30 billion infrastructure and tax-break plan to do just that.