A nearly two-hour press conference may be a sign of presidential endurance, but leaves plenty to critique in the way of mistakes and missteps.

Joe Biden would have been well advised to end the thing at least a half-hour earlier, as by the end he was clearly tired and sometimes losing his train of thought. My sense is that he was determined to show the White House press corps he could stand up there and take their shots until all the questions had been exhausted. Along with the president.

President Biden meets with members of the Infrastructure Implementation Task Force to discuss the Bipartisan Infrastructure Law, in the Cabinet Room at the White House in Washington, Thursday, Jan. 20, 2022. (Associated Press)

To be fair, some of Biden’s earlier answers were focused and forceful. He clearly displayed a command of a range of complicated issues. He wasn’t terribly convincing when he denied overpromising and underdelivering, yet made the best case he could muster given his string of setbacks.

But a couple of gaffes can dominate the post-game coverage in an era where far more people see the clips online – and the perpetual punditry – than watch an afternoon presser.

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And that’s what happened with Ukraine.

Biden was choosing his words so carefully in describing Vladimir Putin’s threat to the former Soviet state, so I was stunned when he started to freelance – and suggested the U.S. might not respond to limited military force.

"It's one thing if it's a minor incursion and then we end up having a fight about what to do and not do, et cetera," Biden said.

And moments later: "My guess is he will move in. He has to do something."

Here was the president of the United States predicting a Russian invasion, and worse, saying all the NATO countries might not be on board on how to respond. It was "cleanup on aisle two" time.

A half-hour after the presser, Jen Psaki rushed out a statement to clarify that any military incursion would be met by "a swift, severe, and united response from the United States and our allies."

And Thursday, Biden used an infrastructure task force meeting to walk back his own remarks: "If any assembled Russian units move across the Ukrainian border, that is an invasion."

It was a stunning blunder by a president who prides himself on knowing many world leaders and has long experience on the international stage.

President Biden speaks during a news conference in the East Room of the White House in Washington, Jan. 19, 2022. (Getty Images)

The other mistake was more nuanced. Biden was talking about the Democratic voting rights bills, which the Senate was in the process of defeating, as everyone expected, during the press conference.

A reporter asked that if the bills failed, "do you still believe the upcoming election will be fairly conducted and its results will be legitimate?"

And Biden equivocated: "Well, it all depends on whether or not we're able to make the case to the American people that some of this is being set up to try to alter the outcome of the election."

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Even sympathetic pundits thought that crossed a line. After more than a year of Donald Trump insisting the 2020 election was rigged, Biden was questioning the legitimacy of the 2022 elections. And his detractors said he was laying the groundwork for explaining away a Democratic wipeout in the midterms.

President Biden answers questions during a news conference in the East Room of the White House on Jan. 19, 2022 in Washington. (Getty Images)

Now from Biden’s point of view, he was decrying Republican efforts to tighten voting restrictions in a number of states, which he views as a partisan threat to democracy. Therefore, he would deem it fair to say we can’t be assured of no improper election meddling unless my legislation passes. (Except that these bills include such liberal wish-list items as making Election Day a holiday and mandating early voting.)

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But he was tone-deaf in not realizing that he was issuing what sounded like a Trumpian warning to voters on the other side, except from a Democratic president.

It may be unfair to judge a press conference by a couple of bad moments, but it’s always been that way – especially when the issue was not a mangled fact but a potential foreign-policy fiasco.

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Still, it was good for Biden to be seen as engaging with all kinds of reporters. I hope he does more of these – though his staff would undoubtedly prefer they be a tad shorter.