If Hillary Clinton wins the United States presidential election in six weeks' time, a great deal of the credit could go to her demeanour in last night's first debate. Facing a candidate who observes few of the conventions of a presidential campaign, including a respect for fact and truth, she not only kept her focus on what needs to be done, she stayed in good humour.
Very good humour. Her manner on the campaign has not always looked genuine but it was last night. She smiled broadly and naturally through his now familiar lines, particularly when he tetchily declared his temperament was up to the job.
That was in response to her reminding him he has threatened to "blow out of the water" a boat whose crew had "taunted" an American naval vessel.
She challenged his fitness to command US military power on much more serious issues, such as making the US commitment to Nato dependent on its allies paying for its protection.
"Words matter," said the former Secretary of State, "they matter when you are President and when you are running for President." And she used the debate to tell America's allies she would not compromise their security.
Overall, the debate exposed the limitations of Donald Trump's solutions to the problems he sees in America. Time and again, when Clinton set out her ideas for what should be done, Trump avoided the question and ran through the relevant lines from his stump speech again. If undecided voters are in a mood for change, this might not matter. But he offered nothing last night that would seem likely to win over voters who are not already enamoured of him.
Clinton delivered some telling blows, on his business dealings and his refusal to make public his tax records as presidential candidates are expected to do. She suggested he had in fact paid no federal taxes and his blustering response could not hide his failure to deny it. He would release his records, he said, when she released emails sent on an insecure phone when Secretary of State. She ignored the challenge, repeated her regret at using a private phone and Trump did not press it.
Americans were probably much more interested in their attitudes to the economy. Trump thinks the US is in "a big fat bubble" that will burst after the election when the Federal Reserve raises interest rates. That might happen if he wins, but the Fed chair Janet Yellen thinks the US economy is gaining strength and her board might have lifted interest rates last week were it not for the uncertainty of the election result.
Trump last night repeated his determination to renegotiate America's trade treaties, and to impose a punitive tax on products made by US firms offshore. Clinton chose not to debate the implications of these proposals for the American economy but they do not bear thinking about. Nor does Trump's plan to drastically lower company tax rates. He proudly compares his cut to Ronald Reagan's, which left federal finances in serious deficit.
Neither candidate would have disappointed their committed voters last night, both needed to appeal to the undecided. From this distance it looked like Clinton's night.