Turns out Iowa is big enough for two presidential candidates when they don’t get too close to each other. Former vice president Joe Biden, who once threatened to take Donald Trump out behind the bleachers and show him a thing or two, spent Tuesday in the eastern part of the first caucus state. Trump—who’s leased a room in his head, rent free, to the former vice president—stayed mostly in the west. Never the twain did meet.

That doesn’t mean there wasn’t a duel at dawn and for the rest of the day. Trump started his trip by attacking Biden, who’d put out an advance copy of his speech at 6 a.m. Biden took Trump to task on the issues: affordable health care, his erratic tariffs crushing Iowa farmers, his MAGA slogan. Forget about making America great again, Biden said; worry about “making it America again.”

And, yes, Biden said “Trump’s an existential threat.” But Trump didn’t go after Biden on any of that. Rather, he went down his preferred low road of personal attacks, going all in on Biden’s physical and mental health, following the path that Fox, either at Trump’s instigation or for its own mischief, travelled over the weekend.

Call it Trump-itis: Every candidate he goes up against is suddenly, in his telling and that of his surrogates, in mental decline and at death’s door. It “happened” to Hillary, who miraculously recovered, and now it’s Biden who’s supposedly moving slower in body and mind. “He’s the weakest mentally, up here,” said Trump—who doesn’t read and routinely leaves meetings in the Oval Office to catch something on the TV always blaring in his study—tapping his finger on his head, careful not to disturb the swirl on top any more than the whirling blades of Marine One were already doing.

“I like running against weak people” Trump added, as he went on to recall that “Joe never got more than 1 percent,” in his prior presidential races and would still be in a “trash heap” if Obama hadn’t come along and rescued him.

That made Tuesday a banner day for Biden, treated as the presumptive candidate by the president who hardly spared a word for the other Democratic hopefuls. Trump’s been told to resist spending so much time on Biden but the president, who can live without a friend but not without an enemy, can’t help himself. He wakes in the morning to go on offense. He prefers the fight be binary. He’d much rather knock off a vice president than one of the lesser souls competing for the nomination. Trump doesn’t waste his time on nobodies.

He didn’t call Biden a “stone, cold loser,” or “dumb as a rock” or “nasty,” but the campaign is young. A smarter president would have gone after Biden’s bad week, highlighted by his abrupt reversal on the Hyde Amendment. Trump could have cast the day—at an ethanol plant and signing a biotechnology order at a renewable energy site—as a presidential visit, except he couldn’t resist taking shots at Biden.

About 150 miles from Biden that night, Trump appeared in Des Moines before a paying audience—although it’s doubtful avowed white supremacist and Republican Rep. Steve King bought a ticket—there to hear an angry man project his temper on to others. He didn’t disappoint:

“These are angry people. Every day the Democrat party is becoming more and more unhinged and more and more extreme. They’re going crazy. Do you love it? I sort of love it.”

You bet he does. He feels at home. A few miles away in Davenport, Biden took his own shots but never got so aggressive as to attack Trump’s temperament, weak mind, or slow gait. If not a higher IQ, Biden generally has a much higher EQ. When a heckler interrupted Biden, he didn’t ask the crowd to “beat the crap out of him” with promises he’d pay any legal fees. When security tried to remove the man, Biden said, “Be nice. This is not a Trump rally.” Biden convinced the questioner to come up front and pipe down, promising him a private conversation later. He also squeezed in a description of a day last weekend with family, including Obama’s, at his granddaughter’s graduation, as much to contrast his normal life with Trump’s as to re-explain his absence from Iowa’s big political dinner over the weekend which 19 nobodies showed up for.

Trump arrived in the Hawkeye State reportedly rattled by internal polls of 17 states by his pollster Tony Fabrizio. They showed him so deep in the hole in red states—four points down in Texas, for instance—that he ordered his aides to lie if asked about the results, according to The New York Times. In a Quinnipiac poll, every top-tier candidate beat Trump in a head-to-head match-up, with Biden clocking him by 13 points. The Times also quoted frustrated campaign aides complaining that he has no interest in a platform or what he would do should he win a second term, preferring the party-planning aspect of the race, like picking the playlist, hats and merch.

One advantage Trump has was on full display in Iowa. He loves being a candidate as much as he hates being president when it doesn’t accord him the perks of a king, with all its pomp and pageantry and ruling by fiat. Most politicians campaign to win the privilege of governing. Trump simply campaigns to campaign, replaying his golden oldie greatest hits. He barely unpacked his golf clubs in the residence before heading off to various Trump properties to swing them while holding rallies nearby complete with “build the wall” and “lock her up” tired chants he should have packed up and put away as the toys of a candidate long ago. He mocked being president, mincing across a stage to imitate what he’d become if he took the office seriously.

There was nothing original about Tuesday. “Sleepy Joe”? His insult-names aren’t sticking any more, and replaying the health card is doomed. How ridiculous for an overweight president who calls for a golf cart to travel 700 yards rather than stroll with his foreign colleagues at a G-7 meeting, and waves a letter from a friend of his father saying he’s in fine fettle instead of releasing his health records, to call Biden out on physical grounds. But we know he’s serious about it. It’s playing nightly on Fox News.

Biden’s biggest strength is his perceived strength, and Trump’s jabs did nothing to crimp that. Biden is the candidate with the best chance of taking back those white working class voters who defected to Trump after voting for him and Obama. Biden should say thank you. No one campaigned harder for him in Iowa than Trump.