Image copyright AP

The road from Cleveland to Philadelphia takes you through the Rust Belt of America, the towns where they once made steel and the hills where they mined the coal.

That territory, between the two convention cities in this presidential year, is where the battle will be fiercest because that's the cradle of discontent.

Two conventions over and angry in different ways.

Donald Trump told Republicans that the country was being destroyed by Democrats - its jobs, its self-respect, even its spirit. But he understood what to do about it.

He knew the system better than anyone else, he told them, so he alone could fix it. And he personalised the contest more sharply than any recent candidate has dared, calling Hillary Clinton corrupt and crooked. "Lock her up!" they chanted from the floor.

The unhappiness seeping through her convention was different, coming from supporters of Bernie Sanders - beaten in the primaries - with some of them still willing to boo her name when their hero urged everyone to get behind her to defeat Trump.

The Sanders army from the left is not unlike Trump's own on the right - driven by a passionate but sometimes inchoate rage at what they call "the establishment", for which Clinton stands as a convenient symbol. The candidate for the way things have been.

Image copyright AP Image caption Hillary Clinton faces a question of trust from electors

So the conventions exposed the candidates' weaknesses.

Trump's capacity for crude verbal brawling - even, some Republicans would whisper to you, demagoguery - and the feeling that he might say anything.

And - even with Obama's oratory and her own masterclass of a speech - Clinton's difficulty in persuading some of the most liberal voices in her party that she is indeed the one to beat him. She spoke after being nominated of making a crack in the glass ceiling that had held women back. But there's another invisible barrier for her campaign: reluctance in many electors to give her trust.

They've now laid it all out. When he's questioned, Trump's answer to how he's going to "make America great again" - the theme of his campaign - is vague, as if explanation is unnecessary. "Just watch me," he says. For Clinton, in her convention speech - a one-woman solution ("I alone can fix it") was wrong and dangerous.

And that deep personal divide is also a sharp fork in the road for Americans. Whether on foreign policy, health care, guns and abortion - perhaps above all on the all-important make-up of the Supreme Court - these two candidates talk about a different kind of country.

Democrats spent the four days reminding Americans of Clinton's life story - the young lawyer who fought segregation, the First Lady who championed liberal causes, the senator and secretary of state. Experience that deserved trust, but it makes her dangerously like a status quo candidate at a moment when people want change. Trump says it's his time - a time to take a chance.

So each heads into the campaign with heavy baggage. Trump's unpredictability and volatility are a handicap. What other candidate would celebrate the suggestion that it was the Russians who'd hacked into Democratic National Committee emails, and suggest that they might do more? Then say the next day he was only joking.

Image copyright Getty Images Image caption Donald Trump faces accusations that he is a demagogue

And for Clinton, the private email server that she used when she was secretary of state is a mistake that she can't shrug off: Republicans say if you can't trust her to handle classified messages, why should you trust her to run the country? She says if you can bait Trump with a tweet would you trust him with nuclear weapons?

We'll see an intensely personal campaign in which one candidate is accused of having not enough experience and the other too much.

That means that the most decisive moments will probably come when they meet in three debates, the first in late September. The irresistible force will meet the immovable object. A confrontation, with nowhere to hide. By the time of the last debate - appropriately in Las Vegas, home of the big fight - we should know which of them has best overcome the doubts of the electorate.

America is more partisan than it used to be and divided more deeply. The minority of voters with open minds will decide this election and, with the set-piece conventions over, it may be those face-to-face encounters that will settle the matter.

The first woman candidate against an opponent with no political experience whatever.

However you look at it, we've seen nothing like this before.

James Naughtie is BBC News Book Editor and presents Bookclub on BBC Radio 4. He was a presenter on the Today programme from 1994 to 2015.