ANN ARBOR, Mich. ― The president who saved the auto industry seven years ago returned to Michigan on Monday, delivering an emotional, blunt message to voters in what’s become a potentially key state for the presidential election.

As several thousand people crammed into stands and on the field of the University of Michigan’s baseball stadium, Obama gave a fiery speech on the final day of campaigning ― a day in which both the candidates are their surrogates are criss-crossing the country in a play for about a half-dozen states whose results could determine who becomes the next president.

Michigan, a state that Democratic presidential candidates have won since 1992, is suddenly high on that list. Whether it’s really in play, however, depends on who you ask, and which evidence you trust.

Polls suggest that Clinton is holding onto a modest but stable lead here, somewhere in the low-to-mid single digits. But strategists worry that the polls may be missing a hidden Trump vote, just as they missed support for Sen. Bernie Sanders (I-Vt.) in March, when he upset Clinton in the state’s Democratic primary.

Of particular concern for Democrats is turnout among African-Americans and young people, whose support Clinton needs to offset Trump’s advantage among white, working-class voters. Just last night, Trump drew yet another huge crowd in Sterling Heights, a northern Detroit suburb.

Obama’s trip here, to one of America’s largest public universities, suggested that his primary mission was to work on young voters. And he certainly played to the students in the crowd.

The president, who has been to Ann Arbor several times while in office, joked that many people in the crowd were probably 10 years old and watching the Disney channel when he first ran for president ― and gave a shout-out to Michigan’s undefeated football team.

And then, on a more serious note, he urged them not to be cynical about whether their votes can make a difference.

But the heart of Obama’s speech was an attempt to undercut Trump’s political strength here. He made a direct appeal to working-class voters, particularly the large number who have ties to the auto industry.

Obama recounted the role he played in saving Chrysler and General Motors in 2009, when their imminent financial collapse threatened not just the auto titans but suppliers and other related business ― with a very high likelihood that their failures would send ripples of economic catastrophe throughout the Midwest.

“To every autoworker on the assembly line, to every small business owner, to every barkeeper and every teacher, I think I’ve earned some credibility here,” Obama said.

From there, Obama lit into Trump as somebody who has very little understanding of working people ― except for housekeepers who clean up after him ― and whose record in business included buying Chinese steel for his hotels.

“Donald Trump isn’t going to be the guy who is going to be looking out for you,” Obama said. “Do not be bamboozled. ... He has never shown any regard for working folks.”

Donald Trump isn’t going to be the guy who is going to be looking out for you. Do not be bamboozled. President Barack Obama

Obama went on to criticize Trump for suggesting, in an interview with the Detroit News, that companies should move jobs to nonunion states with lower wages ― a statement that Trump actually made, although he suggested it as an alternative to the companies shipping jobs to Mexico and other countries.

After attacking Trump, Obama talked about Clinton’s plan to help working people ― by, among other things, raising the minimum wage and launching a massive public works program that would create jobs. And in a reprise of lines he’s given many times before, he praised Clinton’s leadership abilities and personality, contrasting them with Trump’s.

“Over the weekend the campaign took away his Twitter account,” Obama said, referring to a New York Times article published over the weekend. “If your closest advisers don’t trust you to tweet, then how can we trust him with the nuclear codes?”

Obama’s appearance is part of a statewide blitz that began as soon as the polls started to tighten and will end as the presidential campaign comes to an official close on Monday evening. Clinton was in Detroit on Friday and planned to stop near Grand Rapids on Monday afternoon, before heading off to Pennsylvania for her final appearances. Trump is also scheduled to visit Grand Rapids later in the evening.

That appearance will be the final stop on his final day of campaign ― a sign of how important his campaign considers the state. And it makes a lot of sense, given electoral math. Even if Trump manages to win every key battleground state, including Florida and North Carolina, he simply cannot win the electoral college without winning over some states that have voted Democratic in the last few elections.

His best chance to breach Clinton’s “blue wall,” as people are now calling this collection of states, is probably New Hampshire. It has an overwhelmingly white electorate, meaning it also has relatively few voters of color to turn out for Clinton. But New Hampshire can’t put Trump over the top if Clinton wins Nevada, as now seems likely.

That has left Trump and his advisers hunting for votes across the Rust Belt and Great Lakes, where the negative impact of trade on manufacturing jobs has made an indelible political impression ― and where Trump’s base of white, working-class voters exist in relatively large numbers.

Pennsylvania was always high on the list, and will remain there, but the focus on Michigan took much of the political establishment by surprise, since the state hasn’t voted Republican since 1988. And about a week ago, polls showed the margin in Michigan tightening just like it was in every other state.

Does that mean the state is really up for grabs? Democrats insist the answer is no. David Simas, Obama’s political director, told The Huffington Post not to read too much into the last-minute visits ― that the timing is more about the lack of early voting in Michigan (as opposed to Florida or North Carolina, where Obama has been several times) than the tightening of the polls here.

“It’s a matter of blocking off the available paths” to 270 electoral votes, Simas said. Because Trump is coming here, so are Clinton and her allies.

Another Democratic Party strategist familiar with Michigan made similar comments in an interview over the weekend, and said ― among other things ― that Democrats had roughly a 50,000-vote advantage in returned absentee ballots as of a few days ago.

This strategist added that Democrats seemed to do much better than Republicans at getting votes from low-propensity voters ― that is, people who identify as Democrats but haven’t always voted in previous elections.

The strategist attributed the success, in part, to Clinton’s get-out-the-vote operation ― a point that Simas echoed, and said was true around the country. “The GOTV that Brooklyn built is better than what we built for 2012 or 2008,” Simas, who was traveling with Obama, said.

Is that spin? Reality? The answer should be clear in a little over a day.