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(CNN) —  

One week ago, Senate Democrats looked to have been routed – or close to it – by their Republican counterparts.

Democratic incumbents in North Dakota, Indiana and Missouri had all lost. Republicans led in Florida, Nevada, Montana and Arizona. The only “good” news for Democrats was that West Virginia Sen. Joe Manchin (D) had been re-elected in a overwhelmingly Republican state – and even that news wasn’t all that great given that Manchin is anything but a reliable Democratic vote.

Boy, can a week change things.

Late Monday, Rep. Martha McSally (R) conceded defeat to Rep. Kyrsten Sinema (D) in the Arizona Senate race, a pickup for Democrats. It was the latest in a series of positive developments for Senate Democrats over the past week – from come-from-behind wins in Montana and Nevada to an ever-shrinking deficit (and an ongoing recount) in the Florida race between Sen. Bill Nelson (D) and Gov. Rick Scott (R).

At the moment, Democrats have lost a total of one seat from where they were before the 2018 election. The worst they will do is a net loss of two seats – assuming Scott’s 12,000-ish vote lead stands after the recount and appointed Mississippi Sen. Cindy Hyde-Smith, who is doing herself no favors, wins the November 27 runoff against former Rep. Mike Espy (D). The best-case scenario for Democrats – and, to be clear, this is NOT likely – is a net gain of a single seat; that would mean Nelson somehow comes from behind in Florida and Espy wins the runoff in an overwhelmingly Republican state.

Let’s say that at the start of the next Congress Senate Republicans have gained two seats, expanding their majority from 51 to 53 seats. Which is, obviously, good for Republicans because, um, controlling more Senate seats is usually a better thing than a worse one.

But, context! Everyone seems to forget that the 2018 election cycle was a once-in-a-generation sort of map for Republicans. Democrats had to defend 26 seats as compared to just 9 for Republicans. Of those 26 Democratic seats, 10 – 10! – were in states that President Donald Trump won in 2016 including five (Indiana, Missouri, Montana, North Dakota and West Virginia) he won by double digits. When the 2018 cycle began, there was not-crazy talk among Republicans that they had an outside chance at controlling 60 seats – a filibuster-proof majority – at the start of 2019.

From that to a modest gain (at best) is a big, big difference. And the reason that’s important is that the battle for control of the Senate majority isn’t a one-cycle affair. It’s about minimizing your losses in bad cycles (when you have lots and lots of vulnerable seats up) and maximizing your gains in good ones.

Which brings us to the 2020 Senate map, in which 22 Republicans are up for re-election as compared to just 12 Democrats. Two Senate Republicans – Susan Collins of Maine and Cory Gardner of Colorado – will have to win reelection in states that Hillary Clinton won in 2016. Democrats are also likely to target Iowa Sen. Joni Ernst, the Arizona seat (Sen. Jon Kyl is expected to resign sometime in early 2019 and will be replaced by an appointee chosen by Republican Gov. Doug Ducey) and North Carolina Sen. Thom Tillis. For Democrats, Alabama Sen. Doug Jones is their biggest problem, and Republicans may seek to target Michigan Sen. Gary Peters as well.

Go forward even two more years and you see another advantageous map for Democrats. Republicans will be defending 21 seats as compared to just 12 for Democrats. Democrats will take a very hard run at Sen. Pat Toomey in Pennsylvania, Sen. Ron Johnson in Wisconsin and the possible open seat currently held by Iowa’s Sen. Chuck Grassley. Democratic vulnerabilities are somewhat limited, with Nevada Sen. Catherine Cortez Masto and Colorado’s Sen. Michael Bennet on the top of the list.

Here’s the point: If Democrats had lost, say, seven Senate seats in the 2018 election – which was not an impossible thing to imagine back in January 2017 – then the 2020 and 2022 cycles would be about shrinking the GOP majority rather than trying to take back control of the Senate. But with Republicans’ best-case scenario looking like 53 seats, Democrats can now make a plausible case that they can retake the world’s greatest deliberative body as soon as 2020.

If they do, the roots of that success were planted in 2018 – and specifically how the party survived what could have been a generational wipeout that might have taken a decade or more to recover from. In politics, winning is always the goal. But minimizing your losses can be a kind of win too – even if you have to wait for the ultimate reward.