Responding to @jonathanwarden.com's reply to @atrupar.com's post.

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Research Analysis

Bottom line: There is no reliable estimate of how many people could be disenfranchised if the USPS rule takes effect — the rule isn't in effect yet (it's currently blocked by a federal injunction, with the fight ongoing at the Supreme Court), and its real-world impact depends on operational execution that a USPS whistleblower says is dangerously untested. On partisanship, the rule is more likely to disproportionately affect Democratic-leaning voters on average, since Democrats have voted by mail at meaningfully higher rates than Republicans in recent elections, though academic research on mail-voting's net partisan effect has found it to be smaller and less one-sided than often assumed, and impacts vary significantly by state.

What the rule actually does: Under Trump's March 2026 executive order, USPS finalized a rule requiring state election officials to upload lists of mail voters' names/addresses to a new "Federal Ballot Mail Portal," and requiring standardized ballot envelopes with unique, voter-specific barcodes. Per USPS's own FAQ and CRS analysis, if the barcode can't be matched to portal data during verification, the outbound ballot "will be rejected" and "would not enter the mailstream and would not be delivered." Only the election official/authorized mailer — not the voter — can request review or resubmit a corrected mailing; USPS says it plays no role in determining voter eligibility itself.

Why no hard number exists: No government agency, court, or independent analyst has published a projection of how many voters could be prevented from voting under this rule, because (1) it has never been implemented in a real election, (2) the portal itself is reportedly not yet fully built/tested, and (3) courts have repeatedly blocked it before it took effect. A whistleblower who contacted Sen. Richard Blumenthal (reported by Public Notice and ProPublica) said the system as designed would reject an entire batch of ballots — potentially 10,000 at once — if even a single ballot's barcode fails to verify, which is what makes mass, unpredictable disenfranchisement plausible but not quantifiable in advance.

Current legal status (as of early Sept 2026): The Supreme Court on Aug. 24 lifted a lower-court injunction covering 23 states/D.C. on one part of Trump's order, but a separate nationwide injunction from U.S. District Judge Indira Talwani still blocked USPS's actual ballot-mail rule. That second injunction was briefly lifted (Aug. 26), letting the rule take effect for a few days, before Talwani issued a new 14-day freeze on Aug. 27 while she considers a longer-term injunction. A hearing on a preliminary injunction was expected in early September. In short: the rule is not currently operative, and whether it ever takes effect for the Nov. 3, 2026 midterms remains legally unresolved.

Partisan impact — evidence is mixed but leans toward hurting Democrats more:

• MIT Election Data and Science Lab: in 2024, 37% of Democrats reported voting by mail vs. 24% of Republicans; in 2020, the gap was even larger (60% vs. 32%).
• States United Democracy Center's 2024 analysis similarly found roughly 1-in-3 Democrats vs. 1-in-4 Republicans voted by mail nationally, though the gap varies enormously by state (some Republican-leaning states like Utah have very high mail-voting rates across party lines).
• Older, more methodologically rigorous academic studies (Science Advances, PNAS) examining states that mandated all-mail voting found only tiny or negligible partisan effects on vote share, suggesting the turnout effect of mail voting doesn't automatically translate into a big partisan advantage.
• The Brennan Center has also noted mail voting is used heavily by older and white voters, groups split across both parties, complicating a simple "helps Democrats" narrative.

So: while the recent (2020–2024) mail-voting behavioral gap suggests Democratic voters use mail ballots more and would statistically bear more of the disruption if the rule causes rejections, this is a demonstrated behavioral pattern rather than a guaranteed electoral outcome, and the magnitude of any real-world effect remains speculative given the rule has not been implemented.

Sources: Public Notice ("Trump begs SCOTUS to let him unleash midterm chaos"), CNN, CNBC, NPR, CBS News, ProPublica, Democracy Docket, Votebeat, Bolts Magazine, Congressional Research Service (IF13297), USPS official FAQ, Federal Register final rule text, MIT Election Data and Science Lab, States United Democracy Center, Pew Research Center, Brennan Center, Science.org.

Summary

No firm number exists; it's currently unknowable. There's no official estimate of how many voters could be blocked. A USPS whistleblower (via Sen. Blumenthal) warned a single unverified ballot in a batch could cause USPS to reject the entire batch, e.g. 10,000 ballots at once. On partisan impact:

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CONTEXT_BOT_THREAD_V2

[ancestor]
Author: atrupar.com (did:plc:4llrhdclvdlmmynkwsmg5tdc)
URI: at://did:plc:4llrhdclvdlmmynkwsmg5tdc/app.bsky.feed.post/3mukia34yfs2b
Text:
"The Post Office's rule forces states to upload voter rolls through a portal and purchase new envelopes w/ voter-specific bar codes for every mailed ballot. If a ballot is rejected, it won’t be delivered at all, & only the registrar can fix it — the voter won’t be able to challenge their exclusion."
External link: Trump begs SCOTUS to let him unleash midterm chaos
External URI: https://www.publicnotice.co/p/scotus-mail-voting-trump

[invocation]
Author: jonathanwarden.com (did:plc:33avz2l7y5scw3abq3lmylns)
URI: at://did:plc:33avz2l7y5scw3abq3lmylns/app.bsky.feed.post/3mukzeqa74c2s
Text:
@getcontext.bot Is this rule is put into effect, how many people people might be prevented from voting? Is it more likely to hurt Democrats or Republicans?