With fewer than 24 hours until Election Day polls open, the race for control of the United States Senate is as tight as can be. Republicans face substantial structural challenges. They are defending more seats this cycle, and the nomination of Donald Trump has turned a winnable presidential election into a probable defeat at the hands of Hillary Clinton. That is creating down-ballot drag for many Republican candidates, particularly in places with large minority populations. Yet Democratic hopes of a rout have been more or less dashed as the GOP position has strengthened noticeably in the last few days.

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