What would it take to make Oklahoma a blue state?

[Skill and Chance]

Need to somehow get the Oklahoma City/Norman area voting like Austin.  It's not totally crazy, but it would probably take a couple decades.

[Skill and Chance]

As the intersection between the South and the Plains, Oklahoma is a very conservative voting bloc. To even make the state closer under current conditions, the Democrats would have to further develop their conservative wing (already happening IMO with Never Trumpers) while also muscling out environmentalists (pretty much impossible).

Or climate change just recedes as a partisan issue after some late 2020's/early 2030's bipartisan deal.  Very underrated possibility IMO in a world where R's can't win without Florida and somewhat later, D's can't win without Texas.

[Skill and Chance]

Need to somehow get the Oklahoma City/Norman area voting like Austin.  It's not totally crazy, but it would probably take a couple decades.

Tulsa would also need to swing substantially to the left. Even then, those rural areas will be very tough to overcome. Admittedly, Oklahoma is probably close to maxed out for the GOP, but I still expect it to be one of the 5 most Republican states in the country for quite some time. As OP said, it's just so, so conservative in almost every way.

That's true.  They would also need to get Tulsa voting at least like Houston, but that part seems reasonable in the near future. 

IMO I think Dems start getting Houston/Harris County numbers in both OK major metros by 2030 or so, but it stops there and that's still good for safe 55/43ish GOP wins statewide.

[Skill and Chance]

An oil crash and some sort of massive church scandal that causes people to leave Evangelical Protestantism en masse, in rapid succession.

Impossible. The whole thing about being an evangelical protestant is that even if your church is torn apart by scandal or schism, you can just go to another one. Not lose your religion entirely. It’s not like the Catholic Church where it’s all centralized; the pastor of every church is like their own Pope basically. And even then, not like the RCC suffered too badly from their own massive scandal. There is no conceivable way to rapidly get all these people to just totally abandon evangelical Christianity, and even if they did, that still wouldn’t guarantee they’d suddenly become socially liberal Democratic voters. Religion in general is on the decline in this country, and that generational change is what might ultimately liberalize some places over time, but it’s happening slower in states like Oklahoma than others. I’d imagine it would be one of the very last holdout states with a strong evangelical presence, in fact.

Oh and the other thing about evangelical Christianity is that it strongly encourages “evangelism,” i.e. converting people. So that’s another reason why it’s declining slower than mainline Protestantism and Catholicism in the US. Even the people they lose can be replaced with new converts, while those churches don’t put nearly as much emphasis on converting people and thus have older populations that are dying out faster. Plus they are less zealous/conservative as it is.

Yes, to flip a state like Oklahoma, a lot of Evangelicals would need to end up in the Dem coalition while remaining in the faith.  I personally think it's very underrated how many younger Evangelicals are a better cultural fit for the left than the right in the long run, especially the secularizing post-Trump right.  Every day we are moving further and further away from the right wing = traditionalist pro-family alignment of 1980-2010 and there's a significant woke streak developing in certain younger churches. 

I would not be surprised at all to see the Evangelical vote snap to something like 60R/40D the day after SCOTUS overturns Roe and starts upholding red state abortion bans.  Abortion is the only issue keeping a lot of people in the GOP.