My guess is that a 1927/8 depression would be pretty dire, though less severe than 1929's OTL equivalent.
I think that since the depression is slightly milder, the Nazis are a bit less effective. Come the 1932 election I reckon they'd take a fair chunk of the vote, though if the 'democratic' parties can collaborate, Weimar Germany might have a better shot of carrying on TTL.
I agree with you re the Tories in 1929 in this scenario. While it’s tempting to imagine that Labour, with a better result, can govern more effectively, I’m not 100 % sure on that given the OTL division over the economic response to the depression. Also, I wonder what an earlier crash would do to the Liberals? If I remember rightly, 1929 was the year of Lloyd George’s ‘slay the dragon’ campaign. I’d expect that to play better TTL, though whether the vote boost would lead to more Liberals keeping their seats is anyone’s guess-it’s possible the vote split between Labour and Liberal could inadvertently deliver some seats to the conservatives actually.
In the US, Coolidge would still ‘Choose Not To Run’, but depending on when the TTL depression hits exactly, most people would assume his decision was down to the probability of electoral defeat. If the depression starts in earnest after silent Cal’s announcement, any ‘Popper knew there was a depression coming’ type of line (real or otherwise) would be bound to gain more attention amongst conspiracy theorists.
Ironically, Hoover might be the only republican with a chance of winning the 1928 election given his popularity, though it’s still unlikely, so I’m doubtful that he’d run. Assuming Hoover stays out of 1928 in this scenario, I imagine someone like Charles Curtis would end up the nominee, though expect a stronger progressive showing at the GOP convention.
I don’t think Smith gets to be the Democratic nominee in this scenario, he’d probably lose out for many of the reasons he failed in 1924. I can’t see Garner gaining much more traction than he did historically in 1932 either, due to the political reality of the time. Instead, William Gibbs McCadoo would probably make an honest run for the nomination again and would either clinch it himself, or allow someone like Newton Baker or Albert Richie to end up as the compromise nominee. As a wildcard, could it even be possible for Hoover to jump ship at this stage and win as a Democrat? I suspect not, though stranger things have happened.
Come Mar 4th 1929, I think we’d be looking at president Baker, Richie or McCadoo, with a real chance of Hoover winning an upset if he chooses to run for either party.