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Hillary Clinton and Bernie Sanders are expected to draw stark distinctions at the Democratic debate Sunday night

The debate is in Charleston, South Carolina, near the church where nine people were killed last June

Charleston, South Carolina CNN  — 

It’s a real fight now.

First, Hillary Clinton spent months keeping from even uttering Bernie Sanders’ name. Then, the two sparred over Wall Street, gun control and health care in early Democratic debates – but the punches were soft compared to what Republicans were unfurling in what was long the closer and more exciting primary fight.

Now, with the two neck-and-neck in Iowa just two weeks away from the caucuses there, both candidates are squarely focused on each other – and they aren’t holding back their attacks.

Democrats are meeting for their final debate before the Iowa caucuses just a block away from the site of the Charleston church shooting seven months ago. The location lends a new tone to the debate over gun control.

It comes as a health care rift between the two candidates is turning bitter, and Sanders is showing a willingness to take his biggest swipes yet at Clinton over her ties to Wall Street.

Here are five things to watch when Clinton, Sanders and former Maryland Gov. Martin O’Malley debate Sunday night:

Will Sanders go negative?

Sanders released a new TV ad last week portraying Clinton as an ally of Wall Street who thinks she can “take millions from big banks and then tell him what to do.”

Sanders’ camp said that the ad was just playing up policy differences. But when a New Hampshire voter pressed Sanders about it Thursday night, the Vermont senator alluded to a willingness to throw punches.

“If people are distorting my record, as is the case right now, we are going to deal with it, and I have dealt with it, and we will continue to deal with it,” he said.

With new polls showing Sanders either ahead or within striking distance in both Iowa and New Hampshire, he’s wearing a bigger target than ever before.

Can a candidate who’s clearly been uncomfortable launching missiles of his own hit Clinton for her paid speeches and big-money donors? Can he reframe Clinton’s attacks over issues such as health care and turn them against her? The answer could set the tone for the two-week sprint to the Iowa caucuses.

Clinton to press Sanders on guns

You’ve heard Clinton hammer Sanders over his 2005 vote to limit gun manufacturers’ liability.

Get ready for a new attack: “The Charleston loophole.”

The debate will take place next door to the Emanuel African Methodist Episcopal Church, where nine people were killed by a gunman during a prayer service in June – and Clinton won’t be shy about saying Sanders deserves a share of the blame for gun laws that allowed the shooter to obtain his firearm.

Here’s the background: Dylann Roof legally purchased the .45-caliber Glock he used in the Charleston church shooting. But his purchase was only allowed because the FBI wasn’t able to conduct a background check within the legally-mandated three-day waiting period. Had that background check been completed in time, Roof, due to a prior drug conviction, would have been denied the firearm.

Clinton is blaming Sanders for that three-day waiting period.

It’s the result of the 1993 Brady Handgun Violence Prevention Act. Initially, the bill would have included a seven-day waiting period. But Sanders was among the senators who voted for a National Rifle Association-backed amendment that drastically narrowed that window to just 24 hours.

After more negotiations, gun control advocates got that window pushed back up to three days. But they blame supporters of that amendment for having to fight for that three-day waiting period in the first place.

It’s not clear that Roof’s purchase would have been blocked if the FBI had four more days.

But Clinton already showed she’s willing to tear into Sanders over what gun control supporters are calling “the Charleston loophole” in an interview with CNN this week.

“You know, there was a loophole, my opponent voted for it, Senator Sanders, that at the end of three days, business days, you get that gun whether they have finished the background check or not,” she said. “The killer in Charleston who brought that gun, if they had just spent a little more time, it would’ve been discovered, he should not have been able to buy the gun, because he had a federal record.”

How will Sanders pay for his health care plan?

This one’s sure to inspire a debate-stage fight: Sanders’ support for single-payer health care versus Clinton’s preference for tweaks to Obamacare.

In terms of ideology, Sanders might actually be closer to the Democratic base than Clinton. He supports a government-run Medicare-for-all system, which would end private insurance.

A December 2015 Kaiser Family Foundation poll found that 81% of Democrats support a Medicare-for-all system. Clinton herself told MSNBC’s Rachel Maddow on Thursday she supports universal health care “no matter how you get there.”

The problem for Sanders: He hasn’t detailed how much he’d charge Americans in taxes to make it happen.

Sanders has said he’ll reveal those details before Iowa votes. He’s also long argued that new taxes to fund a Medicare-for-all system would be dwarfed by the savings Americans would see as a result of ending private insurance premiums.

Still, Clinton’s bet is that the details of Sanders’ proposal will be problematic enough for a Democratic electorate that might not be in the mood to scrap President Barack Obama’s health care law and fight for something bigger.

In the Maddow interview, Clinton said: “To me, the Affordable Care Act is one of the signature accomplishments, not just of this president, but of the Democratic Party.”

Clinton’s ‘electability’ argument

Clinton has endured a string of news reports in recent days comparing Sanders’ rise in Iowa to then-Illinois Sen. Barack Obama’s in 2008.

It’s not just the polls. Clinton has lapsed into 2008-style language, insisting that Sanders can’t wave a “magic wand” to get his agenda accomplished – just as she told Obama he couldn’t wave a “magic wand” then.

She’s increasingly focused on an argument she hopes will energize Democratic supporters: Electability.

She could make a pitch to liberals that while dating Sanders made sense, they should marry the candidate with a long track record of taking on Republicans.

Sanders, though, has a volley of his own prepared: He’s outperforming Clinton against the Republican front-runners in states such as Iowa and New Hampshire, which are general election battlegrounds.

For Sanders, the challenge he confronts in South Carolina is expanding his base beyond the white, liberal electorates of Iowa and New Hampshire.

Clinton has worked to make that difficult. She toured South Carolina with former Attorney General Eric Holder, a high-ranking Obama ally, and she has always outperformed Sanders among the minority voters who make up much of the Democratic base beyond the overwhelmingly-white Iowa and New Hampshire.

Martin O’Malley

The former Maryland governor has never managed to turn the Democratic primary into a three-way race – he feels farther now than ever from the center of the action.

His polished, generational-change argument has fallen on deaf ears as the left has instead chosen a rumpled 74-year-old who seems incapable of abiding by the political establishment’s rules as its icon.

His cash-strapped campaign accepted public financing, which means he has enough money to get through the Iowa caucuses but nowhere near the money to match Clinton and Sanders on the airwaves.

What that means: If O’Malley has any tricks up his sleeve, Sunday night – with a free, national audience and tons of media attention – is his last, best chance to use them.