You can elect a Congress that will stand up to him in 2026. Step 1: continue primarying out establishment candidates from the Democratic Party, because they're largely complicit. Step 2: Vote for said non-establishment candidates in the general election.

The only challenge will be that the White House and complicit state governments are moving to disenfranchise as many people as possible before then, and likewise the White House will almost surely claim election fraud if Congress flips, and try to invalidate or even interfere with vote-counting.

The establishment Democrats are not complicit in Trump's nonsense. So don't vote for non-establishment candidates in the primary; they're more likely to lose in the general election. If you want to win in the general election, you want as many "normal" Democratic candidates as possible.