This article is from the archive of our partner National Journal

On the last day of the 2014 primaries, a fourth congressional incumbent, Democratic Rep. John Tierney, lost his race for renomination in Massachusetts. Unlike the others, though, Tierney's loss could have a big effect on the general election—potentially boosting his own party's chances of holding his seat.

Before Tierney lost Tuesday to fellow Democrat Seth Moulton, a Marine veteran and first-time political candidate, he was gearing up for a difficult rematch with Republican Richard Tisei, who came within a few thousand votes of unseating Tierney in 2012.

Tierney was weakened by family legal trouble (his wife and brothers-in-law were involved in an offshore-gambling scheme) as well as Congress's general unpopularity, then as well as now, and Tisei was preparing to make another hard run at the Democrat in 2014, when President Obama and Elizabeth Warren wouldn't be topping the ticket in Massachusetts's 6th Congressional District.

While former House Majority Leader Eric Cantor and outgoing GOP Reps. Ralph Hall and Kerry Bentivolio weren't from top-tier battleground districts, Tierney's is one of the few House seats that people expected to be heavily contested this fall.

Obama carried 55 percent of the vote there in 2012, which made it among the more Democratic seats that Republicans were targeting this election year. But Tierney's personal vulnerabilities eroded that advantage.

Now that Tierney's out of the picture, several Democratic and Republican strategists watching the race agreed that Democrats could have an easier time beating Tisei again.

The race isn't a complete slam-dunk for Moulton. Even as Obama carried the district in 2012, former Sen. Scott Brown won 54 percent of the vote there, too, and Tisei is a moderate Republican. Finally, Moulton will have to raise money quickly to recover from the latest primary in the nation, while Tisei has been stockpiling cash without worrying about a primary of his own.

But, Moulton has shown himself to be an unusually gifted fundraiser for a first-time candidate, bringing in more than $1.6 million before his primary—and attracting help from some moneyed outside groups, including VoteVets.

Across the country this year, Democratic retirements have given the party problems, especially in a few red-state Senate races that could become the foundation of a majority-making year for Senate Republicans. But Tierney's loss looks like a rare situation when an incumbent heading for the exit is a boost, not a drag, on his party's prospects.

This article is from the archive of our partner National Journal.

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