Back in the spirit of the thread: the Democrat strategy seems to be failing, for reasons that are glaringly obvious to most people.
No, because of the difference between party membership and voting inclination. For instance in the UK, there are about three times as many Labour party members as Conservative party members (and it was more like four or five times, until the UKIP and Brexit parties melted and their followers flooded back into the Tories). But the Tories are ahead in the polls.
The number of registered Republicans went into significant decline in the GWB years, and not entirely coincidentally, the number of registered independents rose by a similar amount. But despite ditching their party representation, those one-time registered Republicans remain heavily Republican-leaning
voters. Thus there are lots more registered Democrats than registered Republicans, and registered Independents lean substantially Republican in voting intention.
When the Democrats say they want to pick up Republicans, they mean Republican-leaning
voters, not registered party members: because its voters that matter.
* * *
We can also talk about people who describe themselves as "independents" in terms of general affiliation, rather than registration - some 40% of the country. Evidence suggests that most of them aren't, in a way. Of the 40% who call themselves independent, well over half are actually very partisan. They call themselves independents more because they are apathetic or have significantly negative attitudes to politics. That's what's making them disinclined to affiliate with a party, not that they don't strongly lean towards its policies.
We could consider this in terms of the debates on this forum. I'll bet a lot the US progressives here might be reluctant to call themselves Democrats under the circumstances, but they'll go out and vote for the Democratic Party over the Republican Party without any hesitation at all.