Are you sure you want to delete this post?
Okay, I admit to "overthinking" these possible outcomes at times. However, having studied both Mitt Romney and the Mormon church in depth during the 2012 campaign, I feel that that Romney has unfulfilled expectations on his shoulders, both from his wife Ann and the Mormon church.
First, Ann took his 2012 defeat real hard, and she is probably coaxing him to "keep the door wide open". No candidate goes into these campaigns without the support of their wives who often are reluctant, but in Ann's case she wants to be first lady more than Mitt wants to be president. The highly ambitious Ann will never publicly admit that, but she is cut out of the same cloth as Mitt.
Second, the Mormon church is a big business and many of their notable members are CEOs of corporations. The Mormon church desperately wants one of their own at the top of government, and Mitt Romney now is the "chosen one". Jon Huntsman filled that role for a while after Mitt's 2012 defeat, but he didn't get far on the stage with Trump during the 2016 campaign. So now Mitt is back to the head of the Mormon pack.
The Mormon Church has an adversarial relationship with the evangelicals, and with Mike Pence the heir apparent to Donald Trump should he leave office prematurely, the Mormon church would not be comfortable with Pence at the helm of government. Hence the coaxing by the church for Mitt to be ready to run.
Governor Kasich is often mentioned as a likely Republican who could displace Trump from his podium, but while he "mulls over the situation", Mitt Romney is aggressively stepping in to fill the void from Day 1 -- keeping his name in the media's attention at every opportunity -- today and at every time Trump screws up. That could be often.
Sure, the opportunity to run for president may never present itself to Romney if somehow Trump survives to 2020. Romney is 71 years old, a year younger than Trump, so chances for a 2024 run become more remote as the years move on. The year 2020 is it...or never.
Finally, the Democrats do not have a solid front runner. Romney sees the Democratic Party field as rather weak compared to his campaign against the formidable Barack Obama. Furthermore, he is counting on the progressive wing of the party to apply purity tests to rule out any moderates that may provide more formidable opposition with the Independent voters. So having a strong progressive like Bernie Sanders as the Democratic Party front runner would increase Romney's chances with the moderates and independents.
So that's my "overthinking". I'll let it go now. Don't want to do a "Chet".