Heidi M. Przybyla

USA TODAY

Hillary Clinton had hoped Tuesday's primaries in five states in the South and Midwest would cement her grip on the Democratic presidential nomination.

Instead, they’re expected to make clear the race will be a slog for many weeks.

Clinton holds a wide lead in Florida and North Carolina, but recent polls show a tight race in Missouri and Sanders narrowing her advantage in Illinois and Ohio. After the Vermont senator pulled off a surprise victory last week in Michigan, closing a 20-point gap in polls, backers of both candidates expect more gains for Sanders on Tuesday.

“Ohio’s going to be the same,” said Rep. Tim Ryan, D-Ohio, who is backing Clinton. “It’s going to be a tough race down to the wire.”

The Sanders campaign believes a strong showing on Tuesday could lead to momentum in places like Arizona, which holds its primary on March 22, further disproving the Clinton campaign’s contention that the Vermont senator is a regional candidate who appeals mainly to white liberals and working-class northeasterners.

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Even if Sanders pulls off an upset in Ohio or in Illinois — where Clinton was born and raised — her status as the race's front-runner would remain unchanged, given her lead of more than 200 pledged delegates. Delegates are awarded proportionally, and she’s poised to collect the most on Tuesday.

“There are plenty of Democrats and Clinton supporters who wish this nomination would have been wrapped up by now,” said Nathan Gonzales, editor and publisher of the nonpartisan Rothenberg & Gonzales Political Report. “I still believe she will be the nominee. It’s just taking longer than expected, and it’s evidence of a growing divide in the Democratic Party,” he added.

What Tuesday's contests could mean, though, is that Clinton will be forced to spend significantly more time fending off attacks from Sanders as opposed to positioning herself for the general election. This is especially problematic for her on the issue of trade, an emotionally charged topic in industrial Midwestern states and one that Republican front-runner Donald Trump is also emphasizing.

The close competition in states like Illinois and Ohio demonstrates the difficulty Clinton is having in selling her proposals for creating manufacturing jobs versus Sanders’ more visceral focus on previous trade deals many voters believe contributed to the hollowing out of the Rust Belt, such as the North American Free Trade Agreement, which was signed into law by her husband in 1993.

“When you look at the trade deals, NAFTA, CAFTA, Ohio has suffered massive losses,” said Jeff Rusnak, Sanders’ Ohio state director. “There’s not a corner of this state that hasn’t been touched.”

While Clinton points out that she voted against the Central American trade deal as a U.S. senator, she once called the proposed Trans-Pacific Partnership the “gold standard," though she has since opposed it.

“Her record has been really distorted on this,” Kristina Schake, a Clinton communications director, said Monday on MSNBC. “She’s been for some trade deals and against others.”

Sanders is also increasing his focus on Clinton’s Wall Street ties, including calling on her to release transcripts of her paid speeches to big banks.

“If you get $225,000 for a speech it must be an incredibly brilliant speech,” Sanders said in Akron on Monday. “If the speech is that great, she might want to release the transcript and let the American people hear it.”

Meanwhile, during a late-morning Chicago rally on Monday, Clinton urged supporters not to take anything for granted.

“If there is an 'L' stop you can go to or there’s a phone call you can make, if there’s a door you can knock on, if there’s a person you can convince, please do everything you can in the next 24-plus hours," Clinton said at the Chicago Plumbers Union hall.

Michigan exit polls showed her trailing among voters earning between $30,000 and $50,000 a year, the demographic most impacted by manufacturing job losses.

Midwest concerns over income inequality, trade prove a challenge to Clinton

USA TODAY's 2016 Presidential Poll Tracker

Clinton is relying on African-American voters to turn out in greater numbers than they did in Michigan after disappointing participation rates in areas like Detroit. On Sunday, former president Bill Clinton made pitches at two area black churches.

Sanders probably has his best chance in Illinois and Missouri.

Clinton tries to fend off a Sanders Illinois surprise

An NBC News/Wall Street Journal/Marist poll gives Clinton a narrow lead in Illinois — 51% to 45% — while a CBS News survey showed Sanders with a slight edge.

Sanders was in Chicago on Friday and Saturday and he’s also attacking unpopular Mayor Rahm Emanuel, a longtime Clinton ally. Sanders is running ads featuring local public figures, including a school principal, talking about corruption in Chicago politics. Another focuses on the death of Laquan McDonald, the 17-year-old African-American shot and killed by Chicago police in 2014.

“Let me be as clear as I can be,” Sanders said over the weekend. “Based on his disastrous record as mayor the city of Chicago, I do not want Mayor Emanuel’s endorsement if I win the nomination.”

Emanuel did not appear with Clinton at the union hall in Chicago on Monday and has steered clear of the Democratic frontrunner’s campaign events in the city for the last several months.

Clinton has 1,234 total delegates, including so-called superdelegates, more than half the amount needed to clinch the nomination. Sanders has 579.

Her campaign has been sending subtle signals that Sanders risks damaging the party’s chances in November if he continues to bloody her during a protracted primary battle. Both in smaller gatherings and during a recent Fox News forum in Detroit, Clinton has spoken about how difficult it was for her to nudge her supporters toward Barack Obama in 2008.

“When you get through a primary, despite the emotions that are engineered in your supporters, you have to take stock of where you are and who is running on the other side,” she said.

Still, some say there’s no reason for Sanders to stand down anytime soon. “I don’t think Sanders has a lot to lose by continuing his campaign,” said Gonzales.

“He has a larger platform than he’s ever had before for his causes,” he said. Sanders, a longtime independent, “has no real loyalty to the Democratic Party. He’s got plenty of money to run the campaign.”

Contributing: Aamer Madhani reporting from Chicago

Elections 2016 | USA TODAY Network