Traditionally, the candidate at the top of the ticket should boost candidates lower on the ballot. Even if Romney only visited the state once, Rep. Denny Rehberg tried his hardest to link the Montana election to national issues, mentioning Obama at every opportunity and rolling out a last-minute endorsement from Mitt Romney. But neither Rehberg or Rick Hill came close to matching Romney’s success.
Romney’s support represents the votes that a reasonable Republican candidate should have been able to get. But Rehberg fell far short, under-performing Romney by 11 points. . The only two candidates who did worse, Todd Akin and Richard Mourdock, practically gave away their seats with ridiculous comments on rape. .
Rick Hill’s performance wasn’t much better. Hill underperformed Romney by 8 points, more than any other Republican candidate seeking an open seat. The only candidates who did worse were challenging popular governors in West Virginia, Delaware, and Missouri.
The imbalance might not signal the weakness of the Republican candidates, but instead show exceptionally strong Democratic campaigns. One in eight Romney supporters split their tickets, voting for Jon Tester and Steve Bullock.
Sources: The first chart is from the Washington Post. The second is my own.