US President Joe Biden is set to face a pivotal week starting Monday, which will challenge his position both domestically and internationally, as pressure mounts for him to abandon his bid for a second term in the White House. Despite facing calls to withdraw following a poor performance in a debate against his rival Donald Trump last month, which highlighted concerns about his age and ability to serve until 2029, the 81-year-old has so far resisted stepping down. His supporters have cautioned that he must demonstrate more effectively that he is the only candidate capable of defeating Trump in the upcoming elections.

"This week is going to be absolutely critical," Democratic Senator Chris Murphy stated on CNN Sunday. International allies, particularly those in NATO, will also be seeking reassurances as they convene in Washington for a summit this week, with many European nations apprehensive about a potential Trump victory in November. The 78-year-old Republican has frequently criticized the defense alliance, expressed admiration for Russian leader Vladimir Putin, and claimed he could swiftly resolve the conflict in Ukraine.

Following a busy day of campaign activities in Pennsylvania on Sunday, Biden has no scheduled public appearances for Monday, opting instead to prepare for the summit. First Lady Jill Biden, a staunch advocate for the president, will campaign on his behalf in Georgia, Florida, and North Carolina. Meanwhile, Democratic lawmakers will return to Capitol Hill from a brief recess, facing pressure to either support the president or encourage him to withdraw.

The NATO summit, commencing on Tuesday, could mark a critical juncture: Democratic congressmen are anticipated to hold their regular caucus meeting, potentially escalating the dissent that has shadowed Biden since the debate. In recent days, five Democratic lawmakers have openly urged him to exit the race, and prominent party figures like former House Speaker Nancy Pelosi have acknowledged the legitimacy of concerns about his health. On Sunday, four senior congressmen reportedly told party lawmakers during a call that it was time for Biden to step aside.

With the election just four months away, time is running out for any attempt to replace Biden as the nominee, and any signs of open rebellion within the Democrats will be closely watched. For the public, Biden's next significant test under the increasingly harsh media spotlight will be a press conference scheduled for Thursday during the NATO summit. He will resume his campaign trail on Friday, visiting the battleground state of Michigan, before heading to his beachside home in Rehoboth, Delaware.

Biden and his team seem resolute to persist, with the campaign planning an intense schedule for late July, including a surge of TV ads and visits to crucial states. However, disillusioned Democrats warn that the prospect of a second Trump presidency, which includes threats against "the enemy within," poses too high a risk to take any chances.

"There's only one reason" the race between Trump and Biden remains tight, Democratic Representative Adam Schiff commented on NBC Sunday. "And that's the president's age."