Updated 9:52 p.m. |  Rep. John F. Tierney, D-Mass., became the cycle’s first Democratic incumbent to lose a primary Tuesday when he fell to a well-funded challenger in the 6th District.  

Iraq War veteran Seth Moulton was leading Tierney, 51 percent to 40 percent, when The Associated Press called the race for the challenger.  

Moulton now moves on to face former state Sen. Richard Tisei in November in this district, located northeast of Boston. “I look forward to contrasting our vision with that of Richard Tisei’s,” Moulton said in his prepared remarks for his victory speech. “We won’t get fresh thinking and new leadership by sending someone to Washington who was first elected to office when I was just six years old.”  

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Moulton upset Tierney by spending more than $1 million on the race, including attacking the congressman for being ineffective. The challenger made the case he was the more electable Democrat in this district in a general election. The race is rated Tilts Democratic  by Rothenberg Political Report/Roll Call.  

But privately, Democrats argue Moulton is the more palatable candidate to take on Tisei in November.  

Democrats said Tierney was uniquely vulnerable in this district, thanks to an ethics scandal involving an illegal gambling ring run by his brother-in-law. The district voted for President Barack Obama by 11 points in 2012, while Tierney squeaked by with a thin 1-point margin.  

But with Moulton as their nominee, Democrats expressed optimism in their chances to keep the seat in November.  

Even Moulton made that point in his victory speech.  

“Our win tonight says two things,” Moulton said. “First, that we’re fed up with gridlock in Congress. Seriously fed up. And, second, that voters want to keep this seat blue.”  

Tierney is the fourth incumbent to lose in a primary this cycle. Check out Roll Call’s Casualty List for more information.  

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