First Read is a morning briefing from Meet the Press and the NBC Political Unit on the day's most important political stories and why they matter.

Why Clinton’s flip-flop on trade is so unbelievable

Yes, Hillary Clinton’s new opposition to the Trans-Pacific Partnership trade accord cleans up something she needed to do before next week’s first Democratic debate. And, yes, it puts pressure on Vice President Joe Biden getting into the race (because he’d be on the only major candidate in support of TPP). But make no mistake: This flip-flop isn’t believable at all. For starters, there was the time as secretary of state when she said TPP “sets the gold standard in trade agreements.” In her book, “Hard Choices” (which she sent out to all the GOP candidates), she called TPP “the signature economic pillar” of the Obama administration’s strategy in Asia. And then there’s the wiggle room she left for herself, as well as the fact that she hasn’t even fully reviewed the trade accord because it’s not public yet. “I’m continuing to learn about the details of the new Trans-Pacific Partnership, including looking hard at what’s in there to crack down on currency manipulation, which kills American jobs, and to make sure we’re not putting the interests of drug companies ahead of patients and consumers. But based on what I know so far, I can’t support this agreement,” she said in her statement yesterday. And because this opposition is so unbelievable, it feeds every negative stereotype about her -- despite the short-term political benefits.

Why Hillary flipped: to protect her left flank

So why did Clinton flip? It was all about protecting her left flank. As one of us wrote yesterday, Clinton’s newfound opposition to TPP protects her against Bernie Sanders’ challenge (especially before Tuesday’s debate; it helps solidify her support with organized labor; and it makes Biden the only Democrat in favor of the accord (if he gets into the race). But we want to focus on the point about organized labor. As AFL-CIO chief Richard Trumka said on “Meet the Press” last month about Clinton and TPP: “I think if she doesn't take a position on TPP, then you can say she's looking for our vote. If she does take a position on TPP, then she's looking for our support. And the difference is, if you get my vote, I come out on Election Day and I pull the lever. If you've got my support, I get up at 7:00 in the morning, I stuffed 200 envelopes, I make seven calls, I go knock on a few doors, and I get my neighbors all excited about voting for her as well.”

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

And why the reversal didn’t do the Obama administration any favors

Here’s a final point we want to make about Clinton’s new opposition to TPP: It doesn’t do the Obama administration any favors, that’s for sure. Obama and his team face a situation where the entire Democratic '16 field (for now) opposes the TPP accord, which won't make it easier to twist Democratic arms to get congressional ratification. (In fact, it’s the opposite of the situation around the Iran deal, where the party’s ’16 contenders and much of the base SUPPORTED the Iran deal.) This time, the Obama White House will have to get much of its support from Republicans -- just like it did in winning fast-track authority earlier this year. And as House Ways & Means Chairman Paul Ryan suggested on “MTP Daily” yesterday, House Republicans might have some concerns about the TPP accord. There’s still plenty of time to go, but the Obama administration will start the ratification process on shaky ground.

House Republicans hold their conference election for speaker

As NBC’s Alex Moe reports, House Republicans will hold their conference-wide election for speaker today (though the full floor vote for both Democrats and Republicans won’t occur until Oct. 29). Here’s today schedule, per Moe: At 8:00 am ET, the House GOP conference will hold a special meeting for all three candidates for speaker -- Majority Leader Kevin McCarthy, Chairman Jason Chaffetz, and Rep. Daniel Webster -- to address the full conference because during the actual voting session candidates are NOT permitted to address colleagues. Then, at noon ET, the House GOP conference will vote for speaker. To win, a candidate must secure 50% + 1. If no one gets this on the first ballot, the top two candidates move on to a second ballot. It is widely speculated that McCarthy will win on the first ballot so this could go rather quickly. And Moe says that we should have a result around 1:30 pm ET. But the big question is what happens on Oct. 29. If all members are voting, Moe adds, 218 votes are required to elect a Speaker on the floor which means McCarthy can only lose 29 votes that day to win.

But would Boehner need to stick around longer than he wants?

Yet there are two questions to ask: One, if he wins, just how strong (or weak) of a position is McCarthy in -- and how will that affect the business that Congress needs to do later this year? “What was supposed to be a relatively smooth ascension for House Majority Leader Kevin McCarthy (R-CA) has been rocked by his own gaffes, outsider challengers and the threat of an unprecedented floor fight that could undermine efforts to avoid a government shutdown and a historic default on the national debt before the year's end,” Talking Points Memo writes. Two, does a weakened McCarthy mean that outgoing Speaker John Boehner might need to stick around longer than he wants? (He’s supposed to step down on Oct. 30.) As Fox News’ Chad Pergram writes, “What happens if Republicans can’t agree on a Speaker? ‘I’ve never seen anything quite like this,’ murmured one senior House Republican aide. ‘I don’t know how this is going to work out.’ ‘I wouldn't be surprised if we don't get a Speaker until the next Congress,’ predicted one Republican lawmaker who asked to not be identified.”

On Rubio’s missed Senate votes

Two days into Jeb Bush and his campaign leaning heavily into Rubio missed Senate votes, we can say the scrutiny can gotten under Rubio’s skin a bit. And if anything, Team Bush is trying to make the case that Rubio is a man in a hurry -- without any real governing accomplishments. But will the missed Senate votes themselves be a major long-term problem for Rubio? We have our doubts. After all, Rubio has already announced he’s leaving the Senate no matter what come 2016 (he’s not running for re-election).

Click here to sign up for First Read emails. Text FIRST to 622639, to sign up for First Read alerts to your mobile phone. Check us out on Facebook and also on Twitter. Follow us @chucktodd, @mmurraypolitics, @carrienbcnews