WASHINGTON — Ready for another debate double-header?

Tonight and tomorrow bring us the second round of Democratic presidential debates — this time from Detroit — and here’s tonight’s lineup: Bernie Sanders, Elizabeth Warren, Pete Buttigieg, Beto O’Rourke, Amy Klobuchar, Steve Bullock, Tim Ryan, John Hickenlooper, John Delaney and Marianne Williamson.

Given this group, we are watching six storylines.

1. The progressives vs. the pragmatists

It’s Sanders and Warren on the left against those trying to claim the pragmatic center (Klobuchar, Bullock, Ryan, Hickenlooper, Delaney), or those who have staked slightly less liberal positions (Buttigieg, O’Rourke).

2. The electability argument

NBC’s Ali Vitali and Shaquille Brewster report that Sanders and Warren are unlikely to go after one another, but don’t be surprised if “electability” becomes the subtext of how they present their arguments and ideas. Oh, and don’t forget: If Sanders or Warren become president, their party could lose a Senate seat — at least in the short term.

3. The generation gap

While we don’t expect anyone to exclaim “pass the torch,” as recently departed candidate Eric Swalwell did last month, the age differences are striking. You have Sanders (77) and Warren (70), versus O’Rourke (46) and Buttigieg (37).

4. Who will be Sanders’ foil?

Bernie Sanders has been trying to pick fights with Joe Biden and Kamala Harris over health care, but neither opponent is on tonight’s debate stage. And as mentioned above, Sanders is unlikely to go after Warren. So where’s the issue tension — versus O’Rourke on health care (Medicare for All vs. Medicare for America) or Klobuchar (as a proxy for Biden on the public option)?

5. Enter Steve Bullock

We have a new participant in tonight’s debate — Montana Gov. Steve Bullock — and this could be his first and maybe only opportunity to make an impression, given the heightened requirements to make the third round of debates in September.

6. The one-percenters and below

And speaking of those heightened requirements — 130,000 donors, at least 2 percent in four qualifying polls — this debate is make or break for everyone sitting at 1 percent or less in the polls.

Tonight’s debate begins at 8:00 pm ET, and it airs on CNN.

Tomorrow’s debate lineup: Joe Biden, Kamala Harris, Cory Booker, Julián Castro, Andrew Yang, Bill de Blasio, Michael Bennet, Tulsi Gabbard, Kirsten Gillibrand and Jay Inslee.

109 Dems — and counting — support an impeachment inquiry

While we stand by our opinion that Robert Mueller’s congressional testimony didn’t produce a galvanizing moment, the number of Democrats supporting an impeachment inquiry against President Trump has increased to 109, per NBC’s Capitol Hill team.

And 16 have come SINCE the Mueller hearings.

One independent, Rep. Justin Amash of Michigan, has called for an impeachment inquiry against the president.

Shakeup at the DCCC

Amid concerns about the lack of diversity at the Democratic Congressional Campaign Committee, its executive director and five other top staffers announced their resignations and departures on Monday, NBC’s Alex Moe and Rebecca Shabad report.

We can’t remember seeing this kind of shakeup at a congressional campaign arm seven months into a cycle.

Remember, Republicans need to flip fewer than 20 House seats to win back the majority in 2020.

2020 Vision: Four House GOP retirements in a week

While Democrats are experiencing a full-blown staff shakeup at the DCCC, House Republicans saw their fourth retirement in the past week when Rep. Rob Bishop, R-Utah, announced he won’t seek re-election in 2020.

The other three retirements: Reps. Paul Mitchell, R-Mich., Pete Olson, R-Texas, and Martha Roby, R-Ala.

Remember, a party that’s out of power starts seeing retirements like these — because it’s not fun being in the House minority.

On the campaign trail today

Before tonight’s debate, John Delaney holds a roundtable with minority entrepreneurs in Detroit… Jay Inslee (who debates tomorrow) has a roundtable with Islamic leaders in Detroit… And Tom Steyer campaigns in New Hampshire.

Dispatches from NBC’s embeds

Sen. Elizabeth Warren held a town hall in Toledo, Ohio and NBC’s Benjamin Pu reports that the crowd was excited, large and energized.

“I haven’t seen a crowd react like this to Senator Warren ever. They were incredibly energized,” Pu observed. “The campaign was completely unprepared for the turnout – more than two thirds of the folks had to be in overflow. The crowd constantly shouted affirmations and repeatedly stepped on her applause lines by cheering loudly. A really impressive show of support from Ohioans. I think the strength of her economic populist message really shone through tonight.”

Tweet of the day: Can we still be friends?

Data Download: And the number of the day is … 55 percent.

55 percent.

That’s the share of Democrats and Democratic-leaning independents who support building on the existing ACA *rather* than replacing it with a national Medicare-for-All plan, according to a new tracking poll from the Kaiser Family Foundation.

The poll found that 39 percent of Democrats and Dem-leaning independents support the Medicare-for-All replacement. Another 6 percent say they’re not sure.

The Lid: The Big Three in Big 10 Country

Don’t miss the pod from yesterday, when we looked at the importance of Michigan, Pennsylvania and Wisconsin for 2020.

ICYMI: New clips you shouldn’t miss

Here’s our team’s big look at how the Democratic candidates are preparing for this round of debates.

NBC’s Ken Dilanian reports that intelligence officials are warning that Trump’s pick for the new director of national intelligence could politicize the job. (And his confirmation could be rocky, the Washington Post writes.)

In a new op-ed, Rep. Rashida Tlaib writes “While Trump spews hate, I continue to do my job.” (Meanwhile, Rand Paul offered to buy Rep. Ilhan Omar a ticket to Somalia so she’ll “appreciate America more.”)

Here’s the latest with the big shakeup at the DCCC.

TRUMP AGENDA: Hurtin’ the suburbs

Trump’s racial rhetoric is taking a toll with suburban women.

The New York Times writes that Trump is “widening his war on black critics.”

A House Oversight report finds that a group of private companies used White House connections to get backing for a Saudi nuclear power project.

2020: Sanders, Warren take center stage

How will Warren and Sanders handle being on stage together?

Warren is calling for new labor and environmental standards in her latest trade plan.

Kamala Harris is taking criticism from both sides for her new health care proposal.

Jay Inslee’s super PAC will be on the air during the debate.