Mandel vs. Brown will be just the second U.S. Senate rematch in Ohio history; Mandel seeks to become the fifth failed nominee to come back and win a seat.
Only one of the 73 Republican U.S. House members from Trump states with Democratic US Senators on the 2018 ballot has mounted a challenge.
The 10 Trump states with Democratic incumbents have voted for senate nominees from the opposing party of the sitting president 62 percent of the time over the last 50 years.
Only one sitting or ex-secretary of state has won the governorship in Ohio history.
Heller is the only Republican among the 15 U.S. Senators who serve states in which their party holds a minority of U.S. House seats; a dozen (including Heller) are up for reelection in 2018.
Republicans would break a party record if eight U.S. Senate nominees are elected from states voting Democratic for president.
The first term U.S. Senator is enjoying a comfortable lead in the polls, but modern political history suggests he should be doing even better.
Nearly five-dozen U.S. House races in 2016 involve the same two major party candidates from 2014 including one matchup in Missouri with nominees squaring off for the sixth consecutive cycle.
Since 1828, one in six states have cast their Electoral College votes for a candidate who failed to win the support of 50 percent of voters in their state.
Every Ohio U.S. Representative is poised to win reelection in November – the first time incumbents would sweep the state in back-to-back cycles in Ohio history.