When would the assasination have happened. Had the electoral college voted. If it had then there would have been no VP.
Ha! It seems you have a point there!
The electoral college casts it's votes (according to the infallible wikipedia) on the Monday After the second Wednesday in December
http://en.wikipedia.org/wiki/Electoral_College_(United_States)
Now in 1928 that makes the exact date that the Electoral College meets December 17th
1928 Calendar
Going with the OP that states that Hoover in TTL would be assassinated by Argentine anarchists led by Severino Di Giovanni during his visit there, that would put the exact date of his assassination between December 13-15 (
link), Before the Electoral College Votes. Now this would cause a huge upset because it has never happened before. The Electoral College would in all likelihood suspend it's voting until they figure out what to do.
Now it's hard to say what they would have done for sure as this hypothetical event is completely unprecedented in American History. My guess is that the Electoral College suspends their vote until the Republican party can reconvene have a second National Convention and settle on it's nominations for President and Vice President. Once the GOP has settled on it's candidates, the Electoral College will cast their votes and conclude the election.
Or at least that's what I think they would do. Anyone else have any ideas as to how this would all go down?
Assuming that my scenario is plausible, the Republicans would try to hold their convention ASAP. within the next week or so. Now it will probably turn into a messy affair, however I think Curtis has the real upper hand in this situation as he was elected Vice-President by the people. I think that source of popular legitimacy coupled with his efficient backroom dealing in his OTL Senate career will be enough to give him the nomination for President IMO. I doubt anyone but Coolidge could mount a serious challenge to Curtis (though he wouldn't) and even then, face serious public recrimination.
Now the real question would be who would the GOP nominate as Curtis' VP. Considering that Curtis was added to the ticket to counterbalance Hoover's pro-business credentials, I'd wager that the business wing of the GOP would seek to balance Curtis somehow. I'd wager a pretty good choice for them would have been
Alvin T. Fuller, former 2-term governor of Massachusetts and founder of Packard branch in Boston.
Following the controversial Republican convention, the Electoral College casts their ballots in late December. Curtis and Fuller are inaugurated on schedule in March and go on to bear the brunt of the responsibility for the upcoming Great Depression.