Thursday’s clash between Democratic President Joe Biden and Republican ex-President Donald Trump may be the most consequential presidential debate in decades. Biden is desperately seeking momentum amid pervasive concerns about his age and leadership on key foreign and domestic policies. Trump will step onto the stage brimming with confidence, despite his status as the only presidential debate participant ever convicted of a felony. Each candidate has glaring flaws that present their opponent with tremendous opportunity — and risk — if he can take advantage. Stumbles will be hard to erase or replace quickly. The next debate won’t be until September. Thursday's debate is at 9 p.m. Eastern at a CNN studio in Atlanta.