Every presidential cycle, someone wonders whether the election could end with a 269-269 tie in the Electoral College. It hasn’t happened, but the country has come close: in 2000, George W. Bush won 271 electoral votes and Al Gore won 266. (One elector abstained in the final tally.)
Steve Kornacki offered a scenario that doesn’t seem too farfetched, considering recent polls:
https://twitter.com/SteveKornacki/status/776417579636289536
The two parts of that map that seem least likely are Hillary winning one of Nebraska’s electoral votes and Trump winning New Hampshire. In 2008, Obama won Nebraska’s Second District by about 3,000 votes. So far this year, the limited polling in Nebraska shows Trump leading statewide, but we don’t have public polling breaking down that support by district. Hillary seems to be enjoying a small but consistent lead in New Hampshire.
In the case of a 269-269 tie, the U.S. House of Representatives must select the president from among the top three finishers:
The House of Representatives elects the President from the 3 Presidential candidates who received the most Electoral votes. Each state delegation has one vote. The Senate would elect the Vice President from the 2 Vice Presidential candidates with the most Electoral votes. Each Senator would cast one vote for Vice President.
Each state delegation, not each Representative, gets one vote in this process. (Note that the 114th Congress begins January 3, 2017, so the incoming members of Congress would vote, not the current members.) Right now, 33 states have Republican majorities in their House delegation and Democrats have 16. Presumably, the House Republicans would select Donald Trump. Ironically, if Democrats win the Senate, they could select Tim Kaine to be vice president.