(Modified to add the strange Presidential election of 2020:
To provide the alternate perspective rather than just making a fuss, here are the margins in the tipping point states going back to 1832:
Nail-biters = <2%
Close margins = 2-5%
Comfortable margins = 5-10%
Landslides = >10%
Nail-biters
1844 (NY 1.05)
1876 (CO state legislature/SC 0.49) ↑
1880 (NY 1.91)
1884 (NY 0.1)
1888 (NY 1.09)
1916 (CA 0.38) ↑
1948 (IL 0.84) ↑
1960 (MO 0.52)
1976 (WI 1.68) ↑
2000 (FL 0.0092)
2016 (PA/WI; 0.72–0.76) ↑
2020* (WI 0.63) even if Biden won the popular vote by 4.46% nationwide
Close margins
1836* (PA 2.36)
1840 (NJ 3.59)
1848 (PA 3.62)
1856* (TN 4.36) ↑↑
1892 (IL 3.09)
1896 (OH 4.78)
1968 (OH 2.28) ↓
1992 (TN 4.65) ↑
2004 (OH 2.11)
Comfortable margins
1852 (NY 5.21)
1860* (NY 7.4) ↑
1864 (IN 7.0) ↑
1868 (NC 6.80)
1872 (OH 7.09) ↑
1900 (IL 8.39)
1908 (KS 9.58)
1940 (PA 6.89)
1944 (NY 5.01)
1980 (IL 7.93)
1988 (MI 7.9)
1996 (PA 9.2)
2008 (IA 9.53)
2012 (CO 5.37) ↓
Landslides
1832* (ME/LA; 10.67/23.34)
1904 (NJ 18.63)
1912 (NY 12.6)
1920 (RI 31.19)
1924 (NE 17.51)
1928 (IL 14.65)
1932 (IA 17.71)
1936 (OH 20.56)
1952 (MI 11.47)
1956 (FL 14.54)
1964 (OH 25.89)
1972 (ME 22.98)
1984 (MI 18.99)
Those marked with asterisks are those in which the winning candidate would have been held short of a majority of the EC, therefore throwing the election to the House.
Those marked with asterisks are categorized by the state which would have thrown the election to the House. Also listed as an alternate is the state which would have delivered the election to the runner-up (Clay, Frémont, Douglas).
I left off 1828 as I don't yet have congressional district-level data for New York and Maine, which is necessary to determine which state (or possibly CD) tipped the election.
In elections beginning in 2008, nominees have frequently won many states by Reagan-like margins while losing others by Mondale-like margins in 1984. It may not be so remarkable that a nominee wins one state (Massachusetts) by an overwhelming majority and loses another (Alabama) by an overwhelming majority. In elections in which cultural affinity seems to decide more who wins a state or loses a state, demographics are everything. Thus two states that can even look much alike may have such disparities in results as Illinois (Biden winning it by 16.96%) and Indiana (Trump winning it by 16.03%). The difference is that Greater Chicago and Greater Indianapolis, although similar in political orientation, are much difference in size with respect to their states. Urban Indiana (except perhaps Fort Wayne) and urban Illinois vote much the same. Rural Illinois and rural Indiana vote much the same. Illinois does have the older and often more decrepit suburbs.
COVID-19 may have greatly shaped how people voted and did electioneering.
