WASHINGTON (AP) — Three weeks since launching his reelection campaign, President Joe Biden is confronting a sweeping set of problems in his day job that defy easy solutions and are not entirely within his control. If, as his advisers believe, the single best thing Biden can do for his reelection prospects is to govern well, then the coming weeks can pose a near-existential test of his path to a second term. He’s facing a showdown with Congress over the debt limit, chaos at the border as pandemic restrictions ease, and a pivotal foreign trip meant to sustain support for Ukraine and contain a more assertive China in the Indo-Pacific.