Here's a current example of your premise in action:

Prior to AOC's recent primary win, there was a lot of DU commentary from a small posse who professed support for a particular AOC primary challenger--- one who for the past ten years has been clearly and loudly calling for the abolishment of both Medicare and Social Security.

Never mind that these same persons who advocated for someone who's been drooling for years about taking a wrecking ball to Medicare and Social Security are likely themselves beneficiaries of both Medicare and Social Security.

Oh, and lest we forget---Never mind that both of these social programs have long been stalwart components of the Democratic Party platform.

But, hey, never mind all that. It could be Satan himself running against AOC and knuckleheads would support him because...because...ummm...uhh. Oh yeah, because Satan is anti-AOC! Yeah, that's it! So, vote for Satan!

Luckily for all of us...regardless of whether we live in AOC's district or not...lucky for us that her constituents were smart enough to trounce the anti-Medicare, anti-Social Security candidate with a severe ass-whooping by over 70% of their votes.

So, yes, lagomorph777, as evidenced right here in this thread, I'd say your premise about a certain percentage of the population not being ready to vote for ideas that would benefit themselves is entirely accurate.

The flip side of that very same coin, as seen by the anti-AOC posse example above, is the percentage of the population who fairly consistently advocate against their own best interests even when they themselves are already benefitting from and fully taking advantage of Democratic policies put into place to protect those interests.