Sen. Susan Collins (R-Maine) became one of the latest with an op-ed in The Washington Post on Tuesday: "With the passage of time, I have become increasingly dismayed by his constant stream of cruel comments and his inability to admit error or apologize."

When you add in all the Republican officials, past and present, who have endorsed Clinton, we're up to more than two dozen prominent Republicans. And that list is growing nearly daily at this point.

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The question you're probably wondering is: who's next? Here's an updated list of the 10 GOP elected officials who may be the next to either hop off the Trump Train, or take a pass on boarding it at all.

The members of Congress

It's difficult to pick from the dozens and dozens of Republican lawmakers uncomfortably supporting their presidential candidate.

We originally had Rep. Adam Kinzinger (R-Ill.), one of Republicans' leading voices on national security, on this list. And sure enough, after Republicans' convention in July -- and Trump's subsequent fight with the Khan family -- Kinzinger said he wouldn't vote for Trump. Moderate Pennsylvania Republican Rep. Charlie Dent said recently he won't vote for Trump either.

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It's unclear whom Kinzinger and Dent will vote for, but Rep. Richard Hanna (R-N.Y.), a moderate Republican who is retiring this year, recently became the first House GOP lawmaker to say he'll vote for Clinton.

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Rep. Scott Rigell of Virginia, who's also retiring this year, says he'll be voting for the Libertarian presidential nominee, Gary Johnson. Rigell subsequently resigned from his local Republican Party before local rules required he get booted out.

Here are a few other House lawmakers whose struggles on whether to support Trump have been most public.

1. Mike Bishop: The Michigan freshman reluctantly endorsed Trump when it became clear Trump was the only candidate left in the race to endorse. But a month later, top Republican leaders were calling Trump's criticism of Judge Gonzalo Curiel "racist," and Bishop was saying this to the Detroit News: "A lot of folks aren’t comfortable with it, I’m not comfortable with it."

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2. Don Young: Right now, the Alaska congressman belongs to two different camps on Trump: the "anyone-but-Clinton" camp and the camp that's vocal in its disdain for Trump, noted the New York Times's Jennifer Steinhauer. (If the latter were actually a club, South Carolina Sen. Lindsey O. Graham would totally be its president.) Young seems like a potential full-time member, too: "I don’t listen to him and never have,” Young told Steinhauer. “I may vote for myself.”

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3. Mia Love: The first-term Utah lawmaker and rising star skipped the Republican convention, even after she was briefly floated to be on Trump's vice presidential list. She told the Salt Lake Tribune she could see "no upside" to being Trump's VP. During the convention, she told CNN's Jake Tapper that Trump would need "a positive agenda" to get her support, and she hasn't said who she'll vote for in November -- except to say there's no way it will be Hillary Clinton. Love, the first black Republican woman elected to Congress, could be in reelection trouble if Trump performs badly enough in her state.

4. Duncan D. Hunter: His inclusion on this list would have come as a surprise earlier this summer: Hunter has actually been among Trump's top defenders in the House. But after Trump's suggestion that members of the military might have embezzled money in Iraq, it appears that's a role Hunter no longer wants to play. "Everybody's asking me to explain all these things that he said," Hunter said. "Some of these things, I don't know what Donald Trump is thinking. … I don't know where Donald Trump is coming from."

The senators

In June, Sen. Mark Kirk became the first GOP senator to rescind his endorsement of Trump, joining his colleague Ben Sasse of Nebraska in the "Never Trump" camp.

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That same month, Collins — one of the most moderate Republicans in the Senate, told the New Yorker it's unlikely, but she might vote for Clinton. (To say that's a rare phenomenon in modern politics would actually be to understate its rarity.) Now that she's said she won't vote for Trump, it's unclear who she'll back, if anyone.

Here are other senators we're watching:

5. Jeff Flake: The Arizona senator is already one of Trump's most prominent critics — so much so that he may already belong on the un-endorse list. When Trump came to Capitol Hill in July, Flake stood up to him — and made sure to let the media know about it.

"I still hope to support our nominee, [but] it's becoming increasingly difficult to see him making the changes he needs to change," he later said, in an interview Sunday with CBS's "Face the Nation." He also predicted Trump could lose his red-leaning state. Right now, there's a decent chance he's right.

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6. Lisa Murkowski: The Alaska senator said this week she hadn't made up her mind on whether to support Trump, echoing Collins's reasons for not supporting him. "He’s made statements and raised opinions that I certainly can’t defend. In fact, some of them I find offensive," she said.

7. Dan Coats: Another perennial Trump endorsement dodger, the retiring Indiana senator is one of many GOPers who have been forced to give statement after statement condemning one of Trump's statements. And he seems increasingly exasperated about it. Coats has struggled to say whether he trusts Trump with the nuclear codes, and to name one policy position he and Trump agree on.

Coats, for what it's worth, did tell the New York Times he's not okay with changing the GOP convention rules to undermine Trump's nomination. That doesn't mean he supports that nomination.

8. Pat Toomey: There's no denying Trump is putting a lot of vulnerable Republican senators in some very awkward situations and potential electoral trouble, Toomey included. A July Franklin & Marshall poll showed Toomey trailing eight points among registered voters, his biggest deficit yet, while Trump trailed Clinton by 13 in the state.

Of late, the Pennsylvania senator has been among the chamber's most determined avoiders of the Trump nod question. In May, he wrote in a philly.com op-ed saying he was reserving his judgment of Trump, objecting to the candidate's vulgarity in particular. Since then, Trump's said a lot we can presume Toomey doesn't like, and the senator has literally run away reporters in Washington to avoid talking about it.

The governors

Moderate Latino governors, conservative Southern governors, Rust Belt governors. There's no one-size-fits-all profile for a Trump-resistant governor. For now, the list of those who have said no thanks to Trump includes Maryland's Hogan, Massachusetts's Charlie Baker and Michigan's Rick Snyder.

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(Note: We originally had New Mexico Gov. Susana Martinez on this list, given her feud with Trump this spring and the fact that despite her role as the head of the Republican Governors Association she hadn't officially endorsed him. But then she showed up at the convention in Cleveland, all smiles, as she cast her state's vote for Trump. So we're taking her off the list. For now.)

There are others:

9. John Kasich: Trump's former primary opponent hasn't ruled out an endorsement. But the Ohio governor has also compared his relationship with Trump to a divorce. "It's painful," he told MSNBC's "Morning Joe" in June. " …I’m not making any final decision yet, but at this point, I just can’t do it." He hasn't really budged much since.

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In an interview Sunday with CNN's "State of the Union," Kasich predicted Trump could lose his home state — a critical swing state.

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