WASHINGTON — On Tuesday, we released the first round of our NBC News/Marist battleground state polls. And the three states we surveyed — Arizona, Florida and Ohio — may well be the most important ones in the country to watch from now until 2020. As different as these states are in their political history, their economic drivers and their demographic diversity, it’s what they have in common that make them so valuable to track. Here’s what these key states share:

Trump won all three in 2016.

Trump won the traditional presidential swing states of Ohio (51 percent to 43 percent) and Florida (49 percent to 47 percent) as well as the emerging battleground of Arizona (48 percent to 45 percent).

They all host competitive races in 2018.

Arizona, Florida and Ohio will hold some of the nation’s marquee Senate and gubernatorial races — and in Arizona, one of its most high-stakes Senate GOP primaries too.

Democrats lead in the Senate contests, though Florida is within the margin of error.

Our latest round of polling showed Senate Democrats with significant advantages in Ohio — where incumbent Sen. Sherrod Brown leads GOP challenger Jim Renacci by 13 points, 51 percent to 38 percent — and Arizona, where Dem Senate candidate Kyrsten Sinema is ahead of all three potential Republican opponents by double digits. In Florida, it’s a margin of error race, but Democratic incumbent Sen. Bill Nelson may have an edge with 49 percent support compared with 45 percent for GOP Gov. Rick Scott.

Trump’s approval now is between 41%-45% in all three states.

Trump is significantly underwater in his job approval rating in both Arizona (41 percent approve, 47 percent disapprove) and Ohio (42 percent approve, 49 percent disapprove.) It’s closer in Florida, where his approval stands at 45 percent compared with a 46 percent disapproval rate.

Just a third of voters in each state say Trump deserves re-election.

In all three states, fewer than four-in-ten voters say Trump should be reelected; 35 percent in Arizona, 37 percent in Florida and 34 percent in Ohio.

But pluralities give him credit for an improving economy.

Perhaps the best news for Trump in this series of polls was that pluralities in each of the three states — 48 percent in Arizona, 48 percent in Florida and 47 percent in Ohio — believe that the economy has improved and that Trump deserves some credit for it.

All three will be presidential battlegrounds in 2020, representing a total of 58 electoral votes.

The road to the White House has traditionally included plenty of campaign stops in Columbus and the I-4 corridor, but the fast-changing state of Arizona — with its 11 electoral votes — may also end up being one of the hardest-fought battlegrounds in the country.

Yes, Ohio has been drifting redder. Arizona, with its changing demographics, is drifting bluer. And Florida is, well, Florida — with all the political volatility we’ve come to expect. But watch which party wins in two of these three Senate contests, or two of the three governor races — or even sweeps all three in either. That will give us a good sense of where the country’s heading before 2020.

And be sure to watch the independents in these states too

Whenever the president is in a particularly bad spot politically (as in the recent controversy over the separation of migrant families), analysts are quick to note that Trump’s Republican base remains solidly behind him — to the tune of 80 or even 90 percent approval ratings for the president among GOP voters.

And that’s true — but it ignores the fact that while Trump may be shoring up those who identify as Republicans, his approval with independents has eroded badly.

Our latest battleground state polls bear this out. Trump’s approval rating with independents is below 40 percent in all three key states: 36 percent in Arizona, 37 percent in Ohio and 39 percent in Florida. And independents are also favoring Democratic Senate candidates: Sherrod Brown is up 21 points with independents, Sinema leads GOP challenger Martha McSally by 17 points among indies and Nelson is up by nine points among independents over Rick Scott.

Keep in mind: The share of those identifying as Republicans is getting smaller, and the share calling themselves independents is on the rise. Sure, Trump is staying strong with his base — but it’s a shrinking piece of the pie.

On SCOTUS, it’s every Dem senator for themselves.

If Democrats had a hope of stopping Trump’s next court appointee, you’d see a united message from the party about how (and why) to block it. But what we’re seeing now is — not that. The red state Democrats who voted for Neil Gorsuch (Manchin, Donnelly and Heitkamp) are already meeting with the president. Others, like potential 2020 contender Cory Booker, are citing the Mueller investigation as a “conflict of interest” for the president as he picks a Kennedy successor. And still others are citing Mitch McConnell’s “election year” argument when he blocked Merrick Garland in 2016.

Every Democrat seems to be doing what they need to do politically, and Chuck Schumer — at least for now — seems to have lost control of the narrative.

But while there isn’t a united message from Democrats in the Senate, Democratic activists are trying to galvanize the party around health care and abortion rights as rallying cries to block the new nominee. As Dem operative Brian Fallon told the New York Times, Democrats “have to do the work and spend the money to communicate the consequences of what a 5-4 court with a newly installed justice looks like.”

Poll: Two-thirds do not want Roe v. Wade overturned

Here’s the Kaiser Family Foundation with a timely new poll on how the electorate sees Roe v. Wade as a Supreme Court appointment looms: “Conducted prior to the announcement of Supreme Court Justice Anthony Kennedy’s retirement, the poll finds two-thirds of the public do not want to see the Supreme Court overturn Roe v. Wade, while three in ten (29 percent) would like to see the decision overturned. A slim majority (53 percent) of Republicans would like to see Roe v. Wade overturned, while large majorities of Democrats (81 percent), independents (73 percent), and women of reproductive age (74 percent) say they would prefer to see Roe v. Wade stay in place.”

Some perspective on Gowdy’s criticism of the Mueller probe

Yesterday, Republican Rep. Trey Gowdy had this to say to Deputy Attorney General Rod Rosenstein during a House Judiciary Committee hearing: “If you have evidence of wrongdoing by any member of the Trump campaign, present it to the damn grand jury...Whatever you got, finish it the hell up.”

But it’s worth keeping in mind that the Mueller investigation has been going on for a fraction of the time of the Gowdy-led Benghazi investigation. The House Select Committee on Benghazi, which Gowdy chaired, was formed in May 2014. And it ended in December 2016 -- after the election. So it lasted 2 1/2 years, despite producing no indictments, no guilty pleas and no prison sentences.

Compare that with the length of the Mueller probe, which has lasted for just over one year since Mueller was appointed on May 17, 2017. And it has produced multiple indictments, multiple guilty pleas and jail time, including for top members of Trump's 2016 campaign.

Remembering the victims of the Capital Gazette shooting

Here’s the latest on the shooting at the Capital Gazette newspaper, via NBCNews.com: “Officials on Friday charged a man who they say opened fire with a shotgun inside an Annapolis, Maryland, newsroom, killing five people in what police called a "targeted attack." The suspect, Jarrod Ramos, had sued the Capital Gazette newspaper six years ago and lost… The five killed were identified as Wendi Winters, Rebecca Smith, Robert Hiaasen, Gerald Fischman and John McNamara.”

As with every shooting, it was important yesterday to remind ourselves not to jump to conclusions about the motivations behind an attack before all the facts were in. And in this case, reports indicate that the suspect was acting on a personal vendetta rather than politically-charged views. But there’s no denying that the shooting put all journalists on edge, because it was hard not to wonder if it was linked to hostility towards the press generally. We’re living in an age where it’s all too easy to assume that journalists could be the target of political violence. That’s a dark reality, but we have to acknowledge the climate we’re in.