Speaker of the House Tip O’Neill once said, “All politics is local.” That may have been true in Tip O’Neill’s day, but some elections are decisively on national issues — and the Congressional elections this year are overwhelmingly national, just as the elections of 1860 were dominated by one national issue, namely slavery.

In 1860, some abolitionists split the anti-slavery vote by running their own candidate — who had no chance of winning — instead of supporting Abraham Lincoln, who was not pure enough for some abolitionists. Lincoln got just 40 percent of the vote, though that turned out to be enough to win in a crowded field.