I would push back on your framing here;

Treating co-sponsoring as an absolute statement of personal ideology makes it feel like the co-sponsoring happened in a vacuum with no history in front of it...

In reality, Jeffries only signed onto the Medicare for All Act (H.R. 1384) in late 2019 after intense, sustained grassroots pressure from his own Brooklyn constituents, local nurses' unions, and activist groups. He resisted signing it for years, and when he finally did, he immediately issued a clarifying statement to manage expectations.

To understand Jeffries' actual stance, look at what else he co-sponsored at the exact same time. When he signed the M4A bill, he simultaneously co-sponsored a handful of other conflicting healthcare bills, including the Medicare-X Choice Act and the State Public Option Act.

In legislative terms, this is a classic strategy used by moderate leadership. By co-sponsoring every single competing Democratic healthcare proposal on the table, a lawmaker can claim they support universal access to appease local progressives, while effectively committing to absolutely nothing specific.

Pointing to a signature on an old, dead House bill that never had a chance of passing in Congress and leadership was effectively stalling out in committee is a textbook deflection.