Sen. Elizabeth Warren, D-Mass., endorsed Rep. John F. Tierney’s re-election bid at a campaign rally in the Bay State’s 6th District Monday, calling the House Democrat a “tireless champion for Massachusetts families.” “I had the chance to work closely with Congressman Tierney on consumer protection issues years before I ran for the Senate, and I’m very glad to work as his partner in Congress today,” Warren said in a release. “Throughout his career, he has fought hard to strengthen our schools, to improve access to high-quality, affordable education, and to make the kinds of investments that grow our economy in the 6th District and across the Commonwealth.”  

Tierney faces a primary  in September against veteran Seth Moulton and attorney Marisa DeFranco. Moulton has raised more money than Tierney — one of only a few challengers to bring in more bucks than an incumbent this cycle — although the congressman has more cash in the bank.  

Tierney’s district is also top Republican target in November.  

The Democratic nominee will face a rematch with former state Sen. Richard Tisei, who lost to Tierney by a 1-point margin in 2012. President Barack Obama carried the district with 55 percent last cycle.  

Operatives blame Tierney’s slim margin on his proximity to a scandal, in which his wife pleaded guilty to filing false tax returns for her brother, who was indicted for running an illegal gambling ring. Tierney was never tied to the scandal, and the House Ethics Committee dropped its investigation  into him last year.  

The Democratic Congressional Campaign Committee is gearing up for a tough November contest. It reserved more than $1.4 million on Boston-Manchester cable and broadcast in the weeks leading up to the November election. However, those reservations could also be used in nearby competitive races in New Hampshire.  

Massachusetts’ 6th District is rated a Tilts Democratic contest by the Rothenberg Political Report/Roll Call.