Harry Enten of Fivethirtyeight.com offers up five lessons from this year’s election, including that “Party identification is a hell of a drug.” The key point:

This year was the first time ever in which every state that voted for a Democrat for Senate also voted for a Democrat for president, and every state that voted for a Republican for Senate also voted for a Republican for president. The correlation between the percentage of the vote that Democrats running for Senate and the Democrat running for the presidency received in individual states was also a record. It seems that once someone decides to vote for one party in federal elections, they’re more likely than ever to vote for the same party for all levels of federal government.