With some assumptions, I have computed the expected vote for Tom Reed and Tracy Mitrano. The actual vote is strikingly similar to the expected vote.

Assumptions:

• Republicans, Conservatives, and those registered with the Independence Party prefer the Republican Party candidate.
• Democrats and those registered with other parties prefer the Democratic Party candidate.
• Half of those not registered with a party prefer a Democrat and half a Republican.
• Half of non-voters prefer a Democrat and half a Republican.

From the first New NY 23rd article cited:

Democrats and Others: 144 thousand

Republicans, Conservatives and Independence Party: 194 thousand

No Party: 93 thousand

Fifty-one percent of registered voters cast a ballot, so the expected votes for Democratic and Republican candidates can be estimated as the sum of registered voters plus half the unregistered voters times the percentage of registered voters who cast a ballot: 51%:

Expected vote totals:

• Democrat: (144+46)*0.51 = 97 thousand
• Republican: (194+46)*0.51 = 122 thousand

Actual vote totals from the second New NY 23rd article cited:

• Tracy Mitrano: 100 thousand
• Tom Reed: 122 thousand

The correspondence between the expectation and the vote totals is striking; here are some possible conclusions:

• Party affiliation is significant.
• Both candidates did about as expected.
• There was no “blue wave” in 2018 in NY-23.

Based on these results, the idea that either candidate did much better or worse than expected is false.

https://newny23rd.com/2018/04/06/how-republican-is-the-ny-23rd/

https://newny23rd.com/2018/11/07/ny-23-election-results/