evidence: President Biden, in a roughly one-hour long press conference, doubled down on his decision to stay in the race, despite growing calls and doubts from leaders and supporters that he should step down from the ticket, and won’t be able to beat former president Donald Trump in November. [...] Since then, Biden and his team have worked to prove he does have the stamina and mental acuity to run this race, adding campaign stops in Wisconsin, Pennsylvania and later this week in Michigan. He did a television interview that aired in full on ABC News and has another one scheduled on Monday with NBC, and he called in to MSNBC’s Morning Joe this week, too. And Biden has turned defiant, telling his party that he’s staying in the race and it was time to stop talking about whether he should quit. He has received wholehearted support from some important figures in the party — but others have since come out and said they think he will lose to Trump. [...] Despite Biden’s insistence for days that he will stay in the race, some Democrats, including Vermont Sen. Peter Welch, have still called on the president to step aside — and are pointing to Harris as the better option for the party.