Tim Walz is 'nervous' about facing J.D. Vance in next week's vice presidential debate as he hunkers down this weekend to prepare for Tuesday's showdown. The Democratic presidential nominee has fretted to friends he's worried he will let Kamala Harris down, people close to him told CNN. Adding to the pressure is the fact that the debate is likely to be the last marquee showdown between the two presidential tickets before the November 5th election. Harris has accepted CNN's offer for another presidential debate but Donald Trump has not.