Citation needed.
Current polls indicate that "[t]wo-thirds of the public, including majorities of Democrats (86%) and independents (67%), support a law guaranteeing a federal right to abortion."
Source: https://www.kff.org/womens-health-policy/poll-finding/kff-he...
> Even if there's an opinion poll [...] that's effectively moot if they don't vote that way.
Weirdly, your own argument is rendered moot with that assertion. But I agree, it's important for people to vote.
That isn't the way people work. Or voting. Or polls.
People are multidimensional but American Presidential politics forces them into a binary decision. Yet there are numerous reasons why people who support abortion might not vote for Biden. They may support abortion but not believe Biden is a credible choice to defend abortion rights. They may support abortion but vote against Biden to punish the Democratic Party for their response to Dobbs. They may support abortion but reject the Democratic Party altogether. They may support abortion but find activism at the state level more effective, and find other things like Biden's support for Israel more objectionable. They may support abortion but also support Trump, because pro-choice Republicans do exist, and their only options will be to vote Trump or not vote and all. And most people won't even vote at all.
>It may not be what they say or even what they think but it is reflected in what they do.
No. It may be comfortable to see people in such black and white terms, but the premise that unless one votes for Biden, one doesn't support abortion regardless of what else one says and does, is ... not even wrong levels of wrong.
I'm sure 0% of Trump voters would tell a pollster they approve of sexual assault but their actions indicate they do.