These Electoral College raw results include some quirks that might need to be adjusted to understand the relationship between the Senate vote and the presidential map in practice. The Democratic tally includes West Virginia, which has moved sharply away from the party in presidential politics. But it does not include D.C.’s three electoral votes. Nor does it include Wisconsin, where Johnson, who was elected in the GOP’s 2010 landslide, opposed the amendment.
Johnson was the only senator in either party who voted against the bill who is from a state in what I have called “the blue wall”: the 18 states that have voted Democratic in at least the past six consecutive presidential elections. From those states, all 32 Democratic senators plus Republicans Pat Toomey of Pennsylvania, Mark Kirk of Illinois, and Susan Collins of Maine voted for the bill. Johnson’s opposition may be an anomaly for Wisconsin because he is accumulating an unwaveringly conservative voting record that could make it difficult for him to win reelection in 2016, when he must face a presidential-year electorate.
If West Virginia is subtracted from the Democratic column and D.C .and Wisconsin are added, the total Electoral College votes for states that showed support for gun control in the Senate vote rises to 269, just one short of the number needed for victory.
The Republican total needs some adjustment, too. It includes Nevada, where Reid voted against the bill for procedural reasons. But it does not include Arizona, Montana, Indiana, Missouri, South Dakota, and Louisiana, all states that now vote reliably Republican at the presidential level (though Obama carried Indiana in 2008). In the latter four of those states, the Senate vote split on party lines, with one Democratic senator supporting the amendment and one Republican senator opposing it. Arizona’s two Republican senators split, with John McCain backing the amendment and Jeff Flake opposing it; Montana's two Democrats also split on the vote. Removing Nevada and giving the GOP those other six states, raises the Electoral College tally of states skeptical of gun control to 186.
After all these adjustments, this calculation still substantially favors Democrats in the Electoral College. That’s mostly because the states whose senators unified against the measure tend to be smaller than those whose senators unified for it. That comparison is irrelevant in the Senate struggle, but it is vital in the presidential race. Of the states in which both senators opposed the background-check amendment, just three (Tennessee, Georgia, and Texas) possess 10 or more Electoral College votes. That compares to 11 states with 10 or more Electoral College votes whose senators unified in support of the amendment.
The balance was closer on two other key votes during the debate. On the amendment from Sen. Frank Lautenberg, D-N.J., to limit the size of magazine clips, both senators from 17 states representing 219 Electoral College votes supported it; both senators from 21 states representing 188 Electoral College votes voted no. On the amendment from Sen. Dianne Feinstein, D-Calif., to ban assault weapons, both senators from 15 states representing 205 Electoral College votes voted yes, while both senators from 25 states with 209 Electoral College votes (including, notably, Colorado) voted no. In each case, the remaining states split their votes.