Want to ruin a Democratic strategist’s New Year? Bring up President Joe Biden’s popularity problem with younger voters. The strategist may start furiously tap-dancing about this outreach plan or that policy achievement. But she has seen the polling trend line. She has heard the focus groups. She knows that millennials and Gen Zers are not feeling the Biden love. Many are threatening to sit out the 2024 election. Some are flirting with supporting Donald Trump — or a third-party rando. Sign up for