2040s at the earliest but who knows
I could just about see 2032.
2020 - Biden wins in a landslide flipping Texas and Georgia. Democrats also take congress and able to begin to enact much of their agenda.
2024 - Republicans fail to learn the lessons of 2020 and nominate a Trump-like candidate but without his charisma, ability to inspire a devoted core following or to get away with lying so easily. Harris wins the biggest Democratic victory since LBJ (and the biggest overall since Reagan). GOP driven back to the most ultra-conservative states e.g. Wyoming, West Virginia, Arkansas. Democrats continue enacting their policy agenda, a new political era has well and truly dawned.
2028 - Harris easily wins reelection but by a bit smaller margin. The GOP finally realises they have to adjust their platform for the new political reality to appeal to non-white voters and people living in suburbs. However the GOP is still too distrusted and Harris too popular for the party to capture the presidency. The North East does trend sharply Republican with the party flipping New Hampshire and Maine, the South by contrast carries on trending Democratic with the GOP jettisoning religious/race wedge issues.
2032 - The Democrats finally run out of steam (as is inevitable), they've done most of what they set out to, and the electorate is getting sick of them and looking for a change. The GOP nominates a popular, charismatic Northeastern governor who wins the election easily with the memory of the disastrous Trump presidency finally fading from popular consciousness. States such as New Jersey and Connecticut flip GOP for the first time since '88.
