Enviro group ups spending to unseat Mass. Sen. Brown

The mailer, along with a more than $700,000 canvassing initiative, will likely push the group’s spending on the race over the $1 million mark, Nayak said.

LCV’s political action arm has spent more than $5 million so far in this election cycle, already topping its 2010 total, Nayak said.

It has backed Democrats Warren, Rep. Martin HeinrichMartin Trevor HeinrichLive coverage: Sanders rolls out single-payer bill Where Dems stand on Sanders's single-payer bill Trade agency should listen to Congress on solar case MORE (N.M.), former Virginia Gov. Tim KaineTimothy Michael KaineWeek ahead: Crunch time for defense bill’s cyber reforms | Equifax under scrutiny Insurer Anthem to cover bare ObamaCare counties in Virginia Senate votes down Paul's bid to revoke war authorizations MORE, Rep. Chris MurphyChristopher (Chris) Scott MurphySenate Dem: Graham-Cassidy is an 'intellectual and moral garbage truck fire' Dems call for action against Cassidy-Graham ObamaCare repeal Murphy fires back at Trump on filibuster MORE (Conn.) and Sen. Jon TesterJonathan (Jon) TesterFive things to know about Sanders’s single-payer plan Where Dems stand on Sanders's single-payer bill Overnight Regulation: DeVos ignites backlash with rewrite of campus sexual assault policy l EPA power plant rule decision likely this fall | Panel approves Trump financial regulator nominees MORE (Mont.).

Last week, LCV opened up a six-figure campaign against Murphy’s Republican opponent, Linda McMahon. The group also spent $850,000 on a direct-mail effort in Virginia that aims to paint Kaine’s rival, former Sen. George Allen (R-Va.), as a pawn of Big Oil.

The group also has spent $1.5 million on House races attempting to unseat five GOP lawmakers it has dubbed the “Flat Earth Five.” That campaign targets Reps. Ann Marie Buerkle (N.Y.), Dan BenishekDaniel (Dan) Joseph BenishekRepublican groups launch final ad blitz in key House battlegrounds Tea Party class reassesses record Michigan Republican to retire MORE (Mich.), Dan Lungren (Calif.), Quico Canseco (Texas) and Joe Walsh (Ill.).

Nayak said such endeavors would continue through the Nov. 6 election.

“Absolutely,” he said. “We continue to see really stark contrasts between the candidates on our issues in these elections.”

Nayak said he hopes the 150,000 people reached through the mailer will make it “very hard for them to even consider voting for Scott Brown.”

The mailer will emphasize Brown’s vote to sustain oil industry tax breaks, which Nayak said is out of step with most Massachusetts voters.

Nayak noted that a higher turnout is expected in a presidential election year compared with the special election Brown won to replace the late Sen. Ted Kennedy (D-Mass.). He said the mail campaign is necessary to familiarize more of the state’s voters with Brown’s positions and record.

The Hill rates the Massachusetts race as a “toss-up.”