Oh lordy,
even back then Tyler was considered to be a pretty bad president. Although in real life I highly doubt that Jackson would beg the Democrats to nominate a guy who was like one of his bitterest enemies in the South (Tyler was basically an unreconstructed old school Southern Democratic-Republican rich boy who disliked Jackson's populism), in this scenario I see that is about as far as Tyler gets. The man just was not well liked by anybody, Democratic or Whig, and for good reason. Hackish Democrats might stage a walkout and not show up to vote in mass numbers. Without any northern presence on the ticket you would have large disaffection from anti-slavery Democrats (yes they existed), immigrants (especially the Irish, who would feel much less enthused to show out for a Democratic candidate who just four years earlier was a Whig), economic moderates (tariff friendly Democrats, especially from Pennsylvania and other mid-Atlantic states who would see the ticket as too pro-free trade), and probably a couple of other groups I can't think of this early in the day.
I consider this map to be possible:
