Before I get to President Biden, let me tell you about my love for a different presidential candidate.

In 1972, when I was 13 years old, I knocked on doors to canvass for George McGovern, the Democratic senator who wanted to end the Vietnam War. McGovern was an honorable man but was regarded by much of the public as too leftist.

We dismissed skeptics. How could voters instead re-elect a crook like President Richard Nixon? When more sober-minded Democrats pushed to nominate former Vice President Hubert Humphrey, who had the virtue of being electable, the McGovern faithful fought back and Humphrey’s bid collapsed.

At the time of the 1972 Democratic National Convention, McGovern was down 20 points in a Harris poll. But we cheered McGovern and believed in him — until Nixon won that November by a 23-point landslide, carrying 49 states.

So in 2024 will Democrats again be loyal to a flawed candidate who is likely to lose — and whose nomination might well lead to G.O.P. control of both houses of Congress — or will they be loyal to the goals they believe in?

We can’t be sure that Biden will lose just because polls show him behind nationally and in most or all of the battleground states. The betting markets give Biden almost a one-in-five chance of being elected. But they give Trump a two-in-three chance of being elected, and is that a risk that Biden wishes to accept as his legacy?