Hi from CNN, this is Madeleine Thompson with five things you need to know for Tuesday, September 17th. We start with news out of Manhattan federal court that Sean "Diddy" Combs has pleaded not guilty to charges of racketeering conspiracy and sex trafficking. After appearing in court, he was denied bail and taken into custody.

This election season, amid assassination attempts and debate soundbites, it's important to keep an eye on the numbers. Polling shows that a small but mighty section of Americans are undecided on how to vote this Election Day. CNN's Harry Enten explains.

4% in the average of polls, 4% of voters say that they are undecided. That is just half the level that we saw in 2020, well, less than the 10% we saw at this point in 2016, much lower than we're used to. In fact, it's the lowest level of undecideds that we've seen in polling at this point, this entire 21st century. What's the deal? Well, I think this might sort of get at it. 2024 is the most important election of my life. 72% of Trump backers say it is. 70% of Harris backers say it is. But just 24% of undecideds say it is. So the bottom line is they don't actually think there's that much on the line going on here. Of course, there's just 4% of them. But that 4% is going to make all the difference in the world.

Schools in Lebanon will close tomorrow after the pager explosions among Hezbollah members that killed at least nine people and injured nearly 3000. That's according to the state run Lebanese news outlet NNA. Israel is refusing to comment on the explosions, but Hezbollah and the Lebanese government have both blamed Israel for the attack. Former assistant Secretary for Homeland Security Juliette Kayyem told CNN what we know so far.

The details are unknown, but there are there are limited range of possibilities. Hezbollah had moved to an unsophisticated communications platform. They need to communicate to to plan their terrorism. So the irony here is that lack of sophistication led to today because these pagers with their lithium batteries, which which appear to have overheated in some way, we don't know how, then they just detonate. The big question and I've been talking to law enforcement sources in Lebanon is you only have two options. It's either software or hardware. Right. On the Israel question, obviously, they're not going to take credit for it. There is almost no other entity that has both the means, capability and desire to do what happened.

'Speaker Mike Johnson has set up a likely doomed vote tomorrow on a six month GOP government funding plan. Two Republican aides say the expectation is that the vote will fail, which could free up Johnson to explore a plan B. The current bill includes a controversial measure targeting non-citizen voting. It's a nonstarter in the Senate, and Johnson already yanked the bill from the floor last week because of significant opposition from his own party. But Johnson is facing pressure from conservatives and Trump to push the so-called election security bill. Congress has until the end of the month to prevent a government shutdown.

A pipeline fire that began in a Houston suburb yesterday continues to burn. Officials say the blaze melted vehicles, damaged houses and forced evacuations from 100 homes in the area. The incident started Monday morning after an SUV struck a valve for a liquid natural gas pipeline. A local official said once the fire is out, residents likely won't be able to go home until the immediate area cools down. The driver of the SUV that hit the pipeline hasn't been identified, but officials said an initial investigation suggested it's not, quote, terroristic activity. Coming up, this is your brain on pregnancy.

'Most people who've given birth will agree that pregnancy changes the brain, but now researchers are closer to understanding exactly how it happens. In a study in the journal Nature Neuroscience, scientists published one of the first comprehensive maps of this understudied process. And the findings are based on one of the study's authors -- 38 year old professor Dr. Elizabeth R. Chrastil. The researchers studied her starting three weeks before she conceived via in-vitro fertilization until two years after her child's birth. The functional implications of the study aren't known yet, but one researcher said it's an exciting step in the historically ignored field of women's health.

That's all for us. We'll be back at 6 a.m. Eastern.