Keller: Key moments from the Trump-Harris debate

The opinions expressed below are Jon Keller's, not those of WBZ, CBS News or Paramount Global.

BOSTON – The first, and possibly only, presidential debate began with a little bit of gamesmanship, Kamala Harris marching right across the stage to deliver the first pre-debate handshake in years to a somewhat startled Donald Trump.

Economy takes center stage

But it was Harris who seemed more nervous at the start, as Trump hammered away on the economy.

There was no fact-checking help from the ABC News moderators as Trump falsely claimed recent inflation was "the worst in our nation's history." (That dubious distinction goes to the Great Depression, when inflation his 129% in August 1922.)

And Trump, after issuing another whopper ("she's a Marxist"), had Harris on the defensive over the cut-and-pasting of elements of her economic plan from old Biden website postings.

Presidential candidates on abortion

When the debate turned to abortion, the tide turned as well.

Trump offered up an old, false chestnut about some states allowing abortions after birth, and was unpersuasive when he claimed he would veto any attempt to institute a national abortion ban.

Meanwhile, Harris came prepared with well-rehearsed lines like "one does not have to abandon their faith or deeply held beliefs...[to believe] the government - and certainly Donald Trump-  should not be telling a woman what to do with her body."

Trump claims migrants "eating the pets"

And Trump's relatively-calm facial expression and vocal tone gave way to agitation and rally-style yelling as he defaulted to a string of hardcore right-wing talking points, most jarringly the freshly-minted lie about migrants "eating the pets" of their new neighbors.

Trump seemed furious when co-moderator David Muir noted there is no credible confirmation of that rumor, to which Trump could only manage: "I've seen people on television."

This gave Harris a chance to uncork her famous laugh as she ridiculed her adversary: "Talk about extreme," she said.

How will debate impact race?

For the most part, the rest of the encounter followed the same pattern -- an increasingly-angry, sweaty Trump bellowing away about personal grievances while his opponent looked like she swallowed the canary.

It was reminiscent of Trump's Republican National Convention acceptance speech, a disciplined start followed by a spiral into unpresidential bluster and self-aggrandizement.

Will it fundamentally change the course of this race? Perhaps. But champagne-popping Harris supporters would do well to recall that Hillary Clinton was widely seen as a clear winner of her 2016 debates with Trump. And we all know how that one turned out.