Dem
51
GOP
49
There have been many polls showing that many voters don't want a rematch between Joe Biden and Donald Trump. The problem is that Democrats really want Biden and Republicans really want Trump. That naturally leads to Biden vs. Trump. That's just how it works.
Biden doesn't have any serious opponent (Rep. Dean Phillips, DFL-MN, is not a serious opponent). The reason is simple. While enthusiasm for Biden isn't high among Democrats, he is generally acceptable to most of them and there is no other single candidate waiting in the wings. If Biden were to die today, Govs. Gretchen Whitmer (D-MI) and Gavin Newsom (D-CA) would jump in along with Kamala Harris and probably half a dozen or more others. None of these have even 25% support among Democrats. The simple fact is that there is no obvious backup to Biden. Harris is just not so popular that she would be an instant shoo-in. She would have to fight tooth and nail for the nomination, and her performance in 2020 shows that she has the wrong stuff. Biden picked her because he wanted a Black woman for VP and he decided she was the best Black woman he could find.
Trump has a cult-like following. It is very deep. Some of his supporters worship him as a god, but not all. A poll from Suffolk University shows that on a scale of 1 to 10 for enthusiasm, 44% of Republicans gave Trump a 10 vs. 18% of Democrats who gave Biden a 10. However, the average response was similar. Trump got a 7.2 and Biden got a 6.3. Almost identical percentages of Republicans (78%) and Democrats (76%) gave their frontrunner a 5 or more. In simple terms: Republicans want Trump and Democrats want Biden.
The reality is that Democratic voters and Republican voters want different things and their candidates give each group what it wants. Democrats care about policy issues (e.g., abortion and democracy) and Biden's positions are at least acceptable to almost all Democrats. Sure, progressives would prefer Bernie, but he's not running and there is nothing Biden has done that angers progressives. They are just disappointed that he didn't do more, although many of them realize he was two votes short in the Senate to get more done than he did.
In contrast, for the most part, what a lot of Republican voters want more than anything is to "own the libs," to make their blood boil, and to punish them for treating them like a bunch of dumb yahoos. Policy is largely secondary. Yes, many care about abortion and immigration, but all the Republican candidates agree on these policy issues. The only one who really drives the libs into paroxysms of rage is Trump. That is why the base is sticking with him.
So despite everybody saying they don't want Trump vs. Biden, Republicans really do want Trump and Biden is the only Democrat with anywhere near majority support, so we are going to get Trump vs. Biden. (V)