For Michigan, probably more than any state in the country, it comes down to the economy and jobs.

Voters in Tuesday's Michigan primary sent that message, propelling Bernie Sanders to a surprise victory over Hillary Clinton. It was a close race, with the Vermont senator capturing 50% of the vote to 48% for the former secretary of state, but exit polls clearly showed that the economy and jobs were the decisive issues.

Exit polls revealed that about 8 in 10 Democratic Michigan voters said they were either somewhat or very worried about the economy, adding that generally trade had moved U.S. jobs out of the country, CNN reported. Bernie Sanders did particularly well with such voters, as exit polls showed that 6 in 10 voters who said international trade was costing U.S. jobs voted for him.

Clinton's strength was in voters wanting to continue the policies of Barack Obama. Some two-thirds of voters expressing that hope voted for her. Polling before the primary had Clinton with consistent double-digit leads going into Tuesday's voting.

The economy in the Midwestern state is much improved from eight years ago when housing and stock prices were in free fall. Unemployment in Michigan rocketed painfully to nearly 15%.

Yet even as its jobless rate has fallen to 5.1%, wages have stagnated or declined, a problem that transcends economic groups.

Republicans Ted Cruz and Marco Rubio blame taxes and government regulation for sluggish wage growth. GOP frontrunner Donald Trump, who won his contest in Michigan decisively, with Cruz and Ohio Governor John Kasich fighting for second, blames bad trade deals and immigration. Democrats Hillary Clinton and Bernie Sanders counter that Republican unwillingness to work with President Obama is the culprit.

Both Trump and Sanders have been able to appeal to voters with their tough talk on free trade. It's an issue where Sanders and Clinton differ.

Watch Now: Bernie Sanders and Hillary Clinton on free trade

Sanders ties the wage problem to trade agreements with Mexico, China and other countries. Liberalized trade over the past 22 years with Mexico, he argued on Sunday in a debate with Clinton in Flint, Mich. has cost the U.S. more than 800,000 jobs. Changes in trade policies with China, he added, has moved thousands more offshore.

"I was on a picket line in early 1990's against NAFTA [North American Free Trade Agreement] because you didn't need a Ph.D. in economics to understand that American workers should not be forced to compete against people in Mexico making 25 cents an hour," he said before turning to address Clinton. "Your story is for voting for every disastrous trade agreement."

Clinton countered that she'd pulled back from supporting the Obama administration's Trans-Pacific Partnership, a trade alliance with Asian countries that would include Japan, Malaysia and Vietnam. She also made clear that she voted against a Central American Free Trade Agreement as a New York senator.

But some tweaks aside, Clinton has largely held a favorable view on lowering trade tariffs to spur international commerce. She enthusiastically supported her husband's decision to sign NAFTA, initially negotiated by George H.W. Bush, and in an exhaustive mining of her record, CNN.com found 45 instances in which Clinton previously supported the TPP prior to preparing for a presidential run.

Nonetheless, on her campaign website, Clinton steers clear of a definitive statement on trade treaties, opting instead for a broad commitment to advancing U.S. interests abroad.

"Hillary believes in free peoples and free markets," reads her policy page. "As president, she'll invest in partnerships in Latin America, Africa, and Asia with people and nations who share our values and vision for the future."

Clinton's position is shared with the Obama administration, which secured a 2012 trade treaty with South Korea, Panama and Colombia and is bargaining with Republicans for passage of the TPP. (Republicans, save for Trump, have held back their support for TPP until Obama agrees to protections for U.S. pharmaceuticals, tobacco products and financial services.)

But in this election, Clinton is feeling heat from her left. A vigorous argument in favor of free trade could cost her more votes in her race against Sanders. The same goes for Cruz, Rubio and Ohio Gov. John Kasich. In their race against Trump, singing the praises of free trade, an essential tenet of Republican conservatives, could cost them at the polls, where voters are mindful of stagnating wages.

Sanders contends that trade treaties have had the net effect of lowering wages. During the Flint debate, Sanders referenced data from Economic Policy Institute to show that as the U.S. economy fails to create new jobs in manufacturing, once the hallmark of Michigan and Ohio, which votes on March 15, the impact is felt throughout the economy.

Since late-2007, some 2.5 million construction and manufacturing jobs were lost in the U.S., accounting for 77% of total job losses. Since then, 5 million news jobs have been created, but jobs in manufacturing and construction have lagged behind other industries, according to the EPI's Robert E. Scott.

That's concerning given that manufacturing jobs have long set a standard for the rest of the economy, especially in blue-collar work. While wages from newly created jobs pay $23.80 on average, those employed in construction earn $28.01 and in manufacturing receive pay of $28.71. It's s point that Sanders frequently makes in his campaign speeches.

"Sanders is all-in in opposition to the current generation of free trade and investment deals that have been negotiated by the Clinton, Bush and Obama administrations," Scott said in a phone interview from Washington. "Sanders' disagreement with Hillary Clinton gets to the core of these trade agreements -- it's about what they're trying to do."

Investor and economic thinker Steven Rattner in The New York Times further boiled down the numbers: Inflation-adjusted private sector wages have gained an average of 2.5% since 2009. In education, health and information services, pay has increased by more than 3%.

Yet in manufacturing, wages have dropped by 0.8%. In the auto sector, still the backbone of Michigan's economy, the decline is a precipitous 12.7%. Meanwhile, employment in Mexico's auto sector since 2009 has jumped 60% to 589,000 jobs.

"Absent open borders, many of those jobs would have been in America," Rattner wrote.

In her Michigan debate with Sanders, Clinton moved the discussion away from trade treaties to the auto industry bailout. Clinton rightly stated that Sanders voted against the $700 billion funding of the Troubled Asset Relief Program, which went in part to auto makers. However, the Vermont senator countered that he opposed TARP because it was also to be used to bailout the country's largest banks, which he argued was unfair to middle-class taxpayers.

Lacing his message with an attack on immigrants, GOP frontrunner Trump has surged to the top of Republican polls in part because of his opposition to international trade agreements. Trump has succeeded in voicing the frustrations of those who have seen their wages decline over the past 30 years. Leading in polls in Michigan heading into Tuesday's vote, Trump says he'd slap 35% tariffs on Ford cars imported from Mexico.

According to a poll conducted by Monmouth University, Clinton held a 13 point lead over Sanders.