A raft of new polls shows former President Trump is losing juice among core Republican voters — a rare but unmistakable drop in base support that would jeopardize his 2024 comeback bid.

Why it matters: Trump famously boasted in 2016 that he "could stand in the middle of 5th Avenue and shoot somebody and I wouldn’t lose voters." Over the past seven years, Trump's iron grip on the GOP base led many political observers to conclude he may have been right.

Driving the news: A new USA Today/Suffolk poll found Trump's favorability among Republicans dropped from 75% in October to 64% in December — below the 70% threshold generally viewed as a Mendoza line for support within a candidate's own party.

• A Quinnipiac poll out Wednesday puts Trump's favorability among GOP voters right at 70% — his lowest mark in the survey since March 2016.
• And a new Wall Street Journal poll has him at 74% — above the Mendoza line, but a 11% decline since March.
• Equally troubling for the former president: Florida Gov. Ron DeSantis is dominating him in a hypothetical head-to-head primary, leading by 23 points (56%–33%) in the Suffolk poll and 14 points (52%–38%) in the WSJ poll.

The big picture: The conventional wisdom that Trump is the favorite to be the GOP nominee is no longer borne out by the polling data.

• It's a stunning fall from the heights of the Trump presidency, when his approval rating among Republicans peaked at 95% and remained above 90% for much of 2020.
• Even in the aftermath of the Jan. 6 Capitol riot, Trump's support from Republicans in most polls hovered above 70%.

Between the lines: There's an understandable reluctance to downplay Trump's political prospects, given how often he's pulverized the conventional wisdom.

• But his candidates' abysmal record in the midterms and his own weak showing against Biden in public polls make him damaged goods.
• The reason Trump has gone to such lengths to deny the 2020 election results is because he can't allow himself to be seen as a loser — it's political poison with the base.

Reality check: Even if Republicans appear to be moving past Trump, they're not moving past his anti-establishment brand of politics. The WSJ poll finds Trump crushing former Vice President Mike Pence, 63%–28%, in a head-to-head matchup.

• It's why DeSantis is such a formidable potential opponent. Because he's not Trump, he dominates among "somewhat conservative" and moderate Republicans in the WSJ poll. But he also steals some of Trump's support from the MAGA base.
• The ability to peel off support from that base — the key to unseating Trump in a primary — is why DeSantis has steered clear of criticizing Trump's extreme behavior, including his infamous dinner with anti-Semite rapper Ye and white nationalist Nick Fuentes.
• DeSantis will need some of those MAGA supporters to prevail, especially if other traditional GOP candidates draw from the more moderate wings of the party.