I don't think running for a second term had much, if anything, to do with stopping Trump. He's wanted to be president for a long time. Now that he got his goal, would he just give it up after four years without even trying to stay in office longer? I doubt it. Anyone ambitious enough to become president is probably ambitious enough to run for a second term, regardless of circumstances.
The problem for the Democrats is that they don't have any strong candidates (in the electoral sense, regardless of what you think of their qualifications) to substitute for Biden. This is a mess largely of Democrat's own making as they've devoted so much energy and resources to countering Trump and preserving the party establishment, rather than cultivating leaders for subsequent elections.
Whereas in 2020 you had Bernie Sanders (who was arguably stronger than Biden) and other young candidates with fresh voices. Due to party politics with the priorities to defeat Bernie, defeat establishment alternatives, and defeat Trump, the promising slate of future candidates have effectively quit the party. And in their place are the same slate of establishment politicians with little differentiation from Biden and even less name recognition. Whatever alternatives are even more sidelined lack the resources to present as an effective challenger against the Republican nominee.
As for Kamala Harris, her nomination as the VP despite being highly unpopular is the epitome of the whole process. The primary reason Kamala is the VP is as insurance policy in case Biden croaks that corporate friendly policies would be faithfully carried out by an establishment politician.
@Maniuser democrats have a pretty solid list of good candidates now (polis, whitmer, Warnock, list goes on). The problem is that they'd have to run against Biden on a platform of "I'm the same except maybe a bit more moderate and younger", which is too weak a platform to primary an incumbent on, and none of them have intraparty clout to win a silent primary.
(People on the left of the party could challenge Biden from the left, but they'd all crash and burn in the general and probably the primary too, and they know it)
@Maniuser I disagree with the idea that the Democratic party doesn't have options for future elections. Gavin Newsom is basically campaigning for president already, and there's also Buttigieg, Ossoff, Klobuchar, and plenty of others
@Arky The fact that Gavin Newsom is often being talked about as a frontrunner despite a high disapproval rating in the highly Democratic state of Cal largely proves my point. The problem is that the Dem establishment is a sinking ship that barely beat Trump in 2020 and is in a much worse position today. Much of their top priorities of Trump, Ukraine, and 'woke' does not reflect the priorities of the average American, and especially that of the working and middle class.
Compared to 2020, Democrats are dealing with the additional baggage of inflation (which upset many people, including those in the core Dem base), eroding support for Ukraine War, migrant crisis in Dem cities that made many in the party questions their support for immigration policies, and the backlash against woke policies. Outside of the small cohort of political elites and ideological zealots, the erosion of support is broad-based across income and racial groups.
Every candidate you listed are still solidly associated with the party establishment, and many didn't even perform well in 2020. Whereas today there isn't any candidate like Sanders who have the same credentials and resonance with the working class.
On the other hand, the Republican side is far more energized and have picked up more independent voters who are turned off by the aforementioned policies. And the additional charges against Trump will do little to decrease his support, and may increase it as we saw in 2020. The only significant benefit I can think of for Democrats is the abortion issue where Republicans may overreach and turn off voters and energize Democratic base.
@ShakedKoplewitz see my other reply. I agree that the other candidates are mostly similar to Biden, and that's the problem. Many already held up their nose to vote for Biden in 2020, and will be even more hesitant to do so again after all the policy and perceived issues I mentioned.
If the Democrat party establishment platform performed well since 2020, then these candidates may be viable. The problem is that the establishment has been increasingly unpopular since at least 2016. Whatever one thinks of Trump, much of his popularity comes from him being an anti-establishment candidate. Whereas the Democrats purged all of theirs, and continue to cling to this sinking ship.
@Maniuser this doesn't match democrats consistently over performing downballot. As a party they're doing fine on candidate quality, they just have issues with Biden's age (and some with inflation, although for that one they'll just have to wait for it to either go down or become the republican's problem.)
@ShakedKoplewitz Can you provide some info on downballot overperformance? And how far downballot? And this discussion was always about the situation with the Presidential election, same as the poll. And you are not addressing most of the points raised.
@CourierSix yes, both Harry Truman and Lyndon Johnson were eligible to run again and chose not to in the face of bad polling.
@ShakedKoplewitz In older history Polk, Buchanan Hayes and Coolidge all also declined to run for a second term.
I think it's actually more a function of Kamala Harris being a mediocre politician. If he'd gone with someone like whitmer or Warnock who'd be popular in themselves I think he'd be much more pressured (and personally much more willing) to yield the nomination, but with an heir apparent who polls this badly, probably not.