With increased turmoil in the Middle East, a seemingly endless stream of mass shootings and continued racial tension in America, Democratic presidential candidates definitely won't run out of things to talk about in their first primary debate Tuesday in Las Vegas.

But there's so much happening, it can be tough to keep up with it all. Here's a guide to the top 12  issues you'll likely hear about in the debate.

1. 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 -- including front-runner Hillary Rodham Clinton, who has weathered criticism that the former New York senator is too close to Wall Street. First, the candidates agree, 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But a Depression-era financial reform law repealed by President Bill Clinton, the Glass-Steagall Act, is a flashpoint between Clinton and her primary opponents.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. Democratic challengers like 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."

2. 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, has entered the Democratic race staking his candidacy on campaign finance reform, though he failed to meet CNN's polling requirements to appear in Tuesday's debate.

3. College affordability

Debt-free college is another mantra 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. 

4. 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 finished recently finished up. The presidential hopefuls 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. 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 Tuesday's debate, she announced she opposed the deal as it exists, saying that according to what she's seen, it doesn't go far enough to protect American workers' jobs.

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

5. Immigration

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

In 2012, he signed an executive action to protect many young people brought into the country illegally by their parents, and in 2014 he expanded those protections to undocumented parents of U.S. citizens and permanent residents. Both programs are on hold as a Texas-led lawsuit challenging the constitutionality of the actions winds its way through the courts.

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.

6. Climate change and clean energy

The American West is facing an epic drought and simultaneously burning up with what's expected to be yet another record-setting wildfire season -- extreme weather events that climate change activists say is evidence of the negative impacts of shifting weather patterns.

Meanwhile, the United States under Obama has invested heavily in alternative energy forms, such as solar and wind power, as well as expanded its natural gas production, extracted through a controversial process known as fracking, that detractors say pollutes the environment and causes earthquakes.

Democratic officeholders almost all unilaterally agree the government needs to step in to help stop climate change and invest in more clean energy, though former Virginia senator Jim Webb opposes cap-and-trade policies and coal plant regulations.

Relatedly, the next president will likely get to decide whether to build the fourth stage of the Keystone XL pipeline to ship Canadian oil to Nebraska -- a touchstone for environmentalists the administration has so far avoided making a decision on. Clinton, who was involved in negotiations for the pipeline as secretary of state, recently ended a long silence on the issue and said she opposes it. But her more liberal challengers, Sanders and O'Malley, mocked her, pointing out they had long ago said they were against the pipeline.

7. The Islamic State

For the past year, the United States and its allies have ramped up targeted air strikes over Iraq and Syria to disrupt the terrorist group that calls itself the Islamic State, which came to rise amid leadership vacuums in the Middle East in 2013 and '14. The group has beheaded many foreigners, including two American journalists, and controls an estimated one-third of Iraq and Syria. Americans are also trying to train Syrian and Iraqi fighters to battle the Islamic State on the ground. Pentagon officials have recently described this fight against the Islamic State as "a stalemate."

In America, the finger-pointing has begun. 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.

8. The Syrian refugee crisis

After Hungarian officials fired tear gas and water cannons at refugees literally knocking on Western Europe's gates, seeking asylum from war-torn Syria and (to a lesser degree) Iraq, Europe's refugee crisis became an international crisis. Obama has said the United States will take in 10,000 Syrians next year (this year, to date, the United States has resettled fewer than 1,400), while European Union officials bicker over quotas and border fences.

The crisis has reinvigorated debates in Washington about national security and the U.S.'s role in Syria. Obama said the United States and its allies "may have to deal with the source of the problem, which is the ongoing crisis in Syria.”

Clinton has called for an "emergency global gathering" to try to solve the problem, while O'Malley wants the U.S. to accept more than 65,000 refugees by the end of 2016.

Things are so dire, though, that the White House asked Kickstarter to open a campaign in October to raise more than $1.6 million to help refugees.

9. The Iraq War

How and why America got into Iraq more than a decade ago is sure to be re-litigated among Democratic presidential candidates, especially since Clinton is the only U.S. senator among the four current and former senators in the race who originally voted to authorize the U.S. to attack Iraq (although not everyone was in Congress at the time of the vote). It was a vote that haunted her in the 2008 Democratic primary -- she has since apologized -- and could rise again this time around, especially as the Islamic State continues to gain territory there. Long-shot candidate former Rhode Island governor Lincoln Chafee hasn't been shy about criticizing Clinton's original support for the war.

The next president will likely have to decide whether to escalate or draw back on American involvement there. Obama said in July there he has no plans to up the roughly 3,500 non-combatant U.S. troops providing support and training for the struggling Iraqi army. Doing so is not an idea that's gained steam among Democrats in the race, either.

Sanders and Chafee both say the U.S. should roll back its involvement in the Middle East.

10. Policing and racial tensions

Racial tensions between communities and police are dominating national headlines and Democratic candidates's platforms. 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 black. In South Carolina, for instance, Sanders leads Clinton among white voters but trails Clinton by 55 points among African Americans.

11. 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.

Four of the five Democratic candidates agree that it's time the federal government step in to stem all-too-frequent mass shootings. (Webb is more supportive of 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. And a new background checks bill failed in Congress after the 2012 Newtown massacre and hasn't really been resurrected since.

Still, there could be some movement in Congress on gun control in the fall; in August, the Senate's No. 2 Republican, John Cornyn (Tex.), introduced legislation designed to encourage states to send more information about residents with serious mental problems to the federal background-check system.

12. A government shutdown

The Republican-led Congress is in chaos, torn between the small-but-significant hard-line conservative faction of its party and establishment leaders who have yet to successfully find an answer for their antagonists. The intractable debate has left Republicans in the House of Representatives leaderless: Speaker John Boehner (Ohio) announced he's resigning this year to essentially avoid another shutdown, and his likely predecessor, House Majority Leader Kevin McCarthy (Calif.), suddenly took himself out of the running last week, citing his own failure to earn a consensus.

Meanwhile, the clock is ticking to raise the debt ceiling in November to allow the U.S. Treasury to borrow money to pay its debts  and pass a spending bill by Dec. 11, among many other tight deadlines. There's a very real possibility those don't get solved in time and the government could shut down this winter.