(CNN) With 176 days until the Iowa caucuses and a record number of Democratic candidates, the 2020 election is already in full swing. Every Sunday, I will break down the 5 BIG storylines you need to know to understand the upcoming week on the campaign trail. And they're ranked -- so the No. 1 story is the most important of the coming week.

Cory Booker is, objectively, on a roll of late. The New Jersey senator had a star turn in last month's CNN-sponsored debate in Detroit. And he received thunderous applause for his speech at the Iowa Democratic Party's Wing Ding Dinner (more on that below!) last Friday.

All of that, theoretically, should add up to momentum for Booker, right? So far, no. A Monmouth University poll in Iowa released last Thursday showed Booker with just 1% support -- behind candidates like Andrew Yang and Tom Steyer. And the national polling picture is no better for Booker. Of the five national polls released this month, he's not higher than 3% in any of them.

Now, it is true that polling can be a bit of a lagging indicator of actual momentum. And the Monmouth poll came out before Booker even addressed the Wing Ding Dinner.

But if all that is true, then we should expect to see movement in Booker's numbers sometime very soon. If not, it's time to start worrying, if you are a Booker backer. (And, yes, I think "Booker backer" should catch on.)

4. The gun debate goes where?: A week removed from back-to-back mass shootings that left more than 30 people dead in El Paso, Texas, and Dayton, Ohio, the question is: What now?

The short answer is nothing -- in the near-term. Congress is on its August recess -- er, work period -- and President Donald Trump is on vacation in New Jersey. So if anything is going to happen, it won't happen until after Labor Day.

And/but: Wyoming Sen. John Barrasso, a member of the Senate Republican leadership, was skeptical about any new gun legislation on Friday. "I have a lot of concerns about the due process component of (red flag laws) and I don't want to punish law-abiding citizens," he said

3. The Epstein aftermath: The apparent suicide of financier -- and accused serial sex abuser -- Jeffrey Epstein in prison over the weekend is a massive story with huge implications. And that's before the President decided to retweet actor/comedian The apparent suicide of financier -- and accused serial sex abuser -- Jeffrey Epstein in prison over the weekend is a massive story with huge implications. And that's before the President decided to retweet actor/comedian Terrence K. Williams , who claimed without basis that Epstein's death was actually a conspiracy related to former President Bill Clinton and former Secretary of State Hillary Clinton.

Rather than retreat from Trump's controversial retweet, the White House seems to be leaning into it. "I think the President just wants everything to be investigated," senior counselor Kellyanne Conway said on "Fox News Sunday" of Trump's tweets.

Where does this go? Trump's capacity to promote disproven conspiracy theories -- millions of people voted illegally in the 2016 election, former President Barack Obama wasn't born in the United States -- is nearly infinite, especially when you consider the lemmings online willing to scoop up any conspiracy theory and run with it.

The real question is how much noise does Trump want to make over this conspiracy theory? And for how long?

2. It's on in Iowa: While 2020 candidates have been visiting the Hawkeye State for months now, the caucuses picked up speed over the weekend with the opening of the While 2020 candidates have been visiting the Hawkeye State for months now, the caucuses picked up speed over the weekend with the opening of the Iowa State Fair (and its renowned Political Soapbox) and the Democratic Party's Wing Ding Dinner (not a typo).

As The New York Times notes of California Sen. Kamala Harris' five-day bus tour through the state: "By the end of her tour on Monday, Ms. Harris will have made more stops in Iowa on this trip than she did in the entire first half of 2019, according to the Des Moines Register's candidate tracker.

And Harris is far from alone. Starting with his turn atop the Political Soapbox on Tuesday, South Bend, Indiana, Mayor Pete Buttigieg, who received a very positive reception at the Wing Ding Dinner, will be on his own three-day tour of the state.

The frontrunner in Iowa -- just as it is nationally -- remains Joe Biden. But as the Times' Nate Cohn argues , the former vice president has softness in his support in the state, despite visiting it more than any of the other three earliest voting states. A loss for Biden in Iowa could be catastrophic to his inevitability campaign. That's why Harris' reengagement in the state -- and Buttigieg's continued commitment -- are so interesting.

1. The 'Gaffe Machine' warms up: Biden is starting to make the sort of misstatements and impolitic comments that he has long been known for. Or at least, people are starting to notice.

Last Thursday in Iowa, Biden said this : "Poor kids are just as bright and just as talented as white kids." His campaign quickly sought to clarify that the former vice president had misspoken. Then, on Saturday in Iowa, Biden recalled being vice president during the Parkland, Florida shootings -- which occurred on February 14, 2018, more than two years after Biden left office. And let's not forget his debate closing last month, when he urged viewers to call " Joe 30330 ."

This is par for the course for Biden. Throughout his political career he has said things that have gotten him into trouble -- from describing Obama as "clean" and "articulate" to urging a Missouri state senator, who had been paralyzed in a car accident, to stand up . But Biden has never been the frontrunner in a presidential race before. And he's never faced someone like Donald Trump -- the President questioned whether Biden is "mentally fit" to be president over the weekend.

Watch for a series of "gaffe" stories this week. And how the Biden team chooses to react to them.