But let’s assume that it was possible for erstwhile conservatives to join the Democratic Party in sufficient ranks to have serious influence. Even if the influx of conservatives into the Democratic Party served this (in my opinion salutary) function, there would still be serious trade offs. You might try to change the party only to see the party change you. We have already seen how several prominent, erstwhile conservative writers have gradually transformed into liberals (if not progressives) after initially focusing their ire exclusively on Trump.
Functional political parties (including the Democratic Party) have a way of enforcing conformity—especially on issues deemed sacrosanct by the dominant members of their coalition. This was true decades ago when pro-life Democrats like Jesse Jackson and Ted Kennedy (and others, like Joe Biden and Al Gore, who voiced some reservations about abortion) were coerced into changing their views. And this coercion is more evident in today’s world because this is an era of nationalized politics with fully sorted parties.
Largely gone are the conservative Southern Democrats and the liberal Northern Republicans. When push comes to shove and the central debate involves teachers unions not wanting to do their jobs, trans-female athletes competing against biological girls in sports, or even something as banal as banning fracking on federal lands, would conservatives for Biden stand athwart popular opinion or change the subject back to Trump’s admittedly horrific presidency?