Democrat Kyrsten Sinema's Senate victory in Arizona was notable on multiple levels.
Firstly, what was a reliable red state is now very much in play for Democrats in 2020.
While Arizona Governor Doug Ducey won re-election, Democrats snagged the Senate seat and flipped Arizona's 2nd Congressional District.
Look for Arizona to become a battleground state in 2020.
More generally, the West and Southwest (Nevada, Arizona, California, Oregon, Washington, New Mexico) are safely or trending Democratic.
Coupled with Democratic wins in the Rust Belt and Upper Midwest, Republicans outside the South are finding it tough going.
That should be of concern for Senate Republicans on the ballot in 2020 from Maine, Colorado, North Carolina and Arizona - and for US President Donald Trump in trying to put together 270 Electoral College votes in 2020.
Secondly, while the National Republican Senatorial Committee's conduct in casting doubt on the vote-counting process was reprehensible, Ducey, Cindy McCain and Republican candidate Martha McSally behaved appropriately, refusing to join in the anti-democratic process of delegitimising elections that don't go their way.
As a result, there will be no reasonable doubt as to the legitimacy of Sinema's victory - or of McSally's political viability going forward.
Thirdly, the Democrats' win reveals just how miserably Republicans performed in a year in which Democrats held on to or flipped Senate seats in seven states that Trump won in 2016 (Montana, Arizona, West Virginia, Wisconsin, Michigan, Ohio, Pennsylvania).
Republicans, with the most favourable map in a generation, will pick up at most two seats (depending on the outcome in Florida).
Trump might have helped Republicans hold on to the deepest-red states (e.g. Missouri, North Dakota), but his dominating presence in the last week or so of the campaign hammering an anti-immigrant message might have harmed House and Senate Republicans everywhere else. (As of this writing, Democrats picked up at least 32 seats; that total could reach 40. They also added at least seven governorships.)
Fourthly, how McSally lost is as important as the loss itself. The Post reports, "McSally lost the race after abandoning the moderate profile she had nurtured in her 2014 congressional race and allying herself with Trump. The former Air Force combat pilot adopted an aggressive tone, accusing Sinema of supporting treason over her 2003 remark that it was 'fine' if a radio host who was asking her a question joined the Taliban."
The lesson here for Republicans should be that unless you are in deep-red states, waving the bloody flag on immigration is a loser.
Fifthly, exits polls in the race showed Sinema hung on to a high percentage of white voters (44 per cent) and won big with Hispanics (69 per cent), white college graduates (53 per cent), white college-educated women (55 per cent), voters 18 to 44 years old (59 per cent), and voters who ranked healthcare as the most important issue (77 per cent).
That sort of coalition succeeded for Democrats in a previously red state - and in races all across the country.
When looking at presidential candidates, Democratic primary voters should consider who has the ability to put together that kind of coalition.
In sum, a week after the Midterms, the Democrats' wins look more impressive - and the GOP looks more like a party in decline. Republicans outside the Deep South should be concerned about their survival so long as Trump is president.