Order all the 2024 Senate races by the Democrat's margin of victory (i.e. % D vote - % R vote).* Which Senate race is the one that would give Democrats their 50th seat?
Here's an example:
Democrats win all seats considered Solid D, plus MD, AZ, NV, PA, WI, MI, by a large margin. (This, plus the D seats that aren't being contested, brings them to 48 seats.)
Republicans win all seats considered Solid R by a large margin. (That's 48 seats.)
The remaining 5 seats are: OH (D+2), MT (R+4), TX (R+5), FL (R+7).
Since Montana is the 50th seat by Democratic margin of victory (at -4), the market would resolve to "Montana".
Just for the purpose of reducing ambiguity, I will ignore deaths and resignations in the Senate. For example, if a Republican senator dies in a state with a Democratic governor (and so their replacement is likely to be a Democrat), that will not affect how this market gets resolved.
Note that I'm asking about the 50th seat -- that is, the seat that would give Democrats the majority, were they to win the (vice) presidency. That's because I think it's very likely that Democrats win the vice presidency conditional on the Senate being close enough for this question to matter.
EDIT: For the purposes of this market, Dan Osborn (I-NE) counts as a Democrat.
*People count as the party they're associated with, e.g. Bernie Sanders is a Democrat.
1,000
3.00@EricNeyman All the close states (PA, OH, NE, MT, TX) have certified their results, so this can resolve to Nebraska now.
47 D Seats
PA: R+0.22%
OH: R+4%
NE: 499,124-436,493=62,631/935,617=R+6.694%
MT: 319,682-276,305=43,377/607,262=R+7.143%
TX: R+8.4%
@nikki Oh oops, that's an embarrassing oversight on my end. And I actually need to figure out whether to count Osborn as a Democrat now, because whether he's a Democrat can matter for this question even if he loses.
I'm tempted to issue the clarification that, for the purposes of this question, Osborn is a Democrat. (This is based on the fact that he's running against a Republican, and if forced to guess now, I would guess that Osborn is more likely to caucus with the Democrats than with the Republicans.
I'll give people 2 days to voice objections to this clarification. If no one voices objections in the next 2 days, I will make this clarification/change to the rules.
@SemioticRivalry Ah yup, I forgot to clarify. I'm specifically asking what would be the 50th Democratic seat, basically because I think in the world where it matters, it's very likely that Walz is the VP. So even if Trump wins, I'm still asking about which seat would get Democrats to 50, not 51.