As almost all of the 20 or so Democratic 2020 candidates prepared to speak at the Iowa Democratic Party's annual summer fundraiser, the 76-year-old said he was unable to attend because of family reasons, but will visit the state later in the week.
The dinner, which informally marks the start of the campaign for the Iowa primary or caucus, which takes place on February 3 and represents the first the public gets to vote on candidates, is taking place as a well-regarded poll by the Des Moines Register, showed Mr Biden’s support slipping in the state.
While Mr Biden still leads the pack on 24 per cent, with Bernie Sanders in second place on 16, the poll shows support for Elizabeth Warren has soared. She is now in fourth place on 14 points, behind third-placed Pete Buttigieg on 15. Some reports pointed out Mr Sanders, Mr Buttigieg and Ms Warren were statistically tied in second place behind Mr Biden.
The slip in the vice president’s lead comes after what he suffered what was widely considered a damaging week on the campaign trail. His campaign initially said the former senator still supported the so-called Hyde Amendment, which bans the use of federal funds to provide abortion services.
But amid an outcry from activists, particularly some powerful women’s groups, Mr Biden declared his view had changed. He said he had changed position in light of the series of draconian anti-abortion measures being passed across the country, but many saw it simply as political flip-flopping. Some wondered how many more “adjustments” the centrist will have to make as he is attacked by more progressive candidates as the primary contest gathers pace.
The poll was conducted between June 2-5, before Mr Biden felt obliged to change his views on abortion. But the results, published over the weekend, added to the narrative of a candidate whose campaign may already be starting to show some cracks
“We’re starting to see the people who are planning to caucus start to solidify,“ said Ann Selzer, of Des Moines-based Selzer and Co, which conducted the poll. “There’s a lot more commitment than we normally see this early. And some of these candidates who’ve been under the radar start to surface and compete with Joe Biden.”
She described Ms Warren’s numbers as “a strong showing”.
“I think that all of the publicity lately and all of the polls lately are so Biden-heavy that for her to have any metric that shows her on par (with him)...it says to me there are people who are paying attention,” she told the Register. “Again, in a field this big, that’s step one. First, you have to get people to pay attention.”
The poll put senator Kamala Harris at seven points, with senator Amy Klobuchar and former Texas congressman Beto O’Rourke both at two points. Seven candidates registered one per cent.
Ms Selzer said many candidates in the large field had failed to make a breakthrough. Nine did not register any support in the poll.
“There's always been a question mark as to how many can get any real traction,” she said.
On Sunday, almost 20 candidates were scheduled to gather at Cedar Rapids, Iowa, for the state party dinner that will feature 15-minute speeches to party leaders and potential voters.