On the day his group began saturating Maine’s 2nd Congressional District with television ads, the congressman who is chairing Republican efforts called the district a top opportunity to pick up a House seat for his party.

On Tuesday, the National Republican Congressional Committee, the campaign arm for House Republicans, kicked off a $1.5 million ad campaign to aid Republican Bruce Poliquin in his run against Democrat Emily Cain for the seat now held by U.S. Rep. Mike Michaud, a Democrat who is running for governor.

The committee has spent that much or more on only one race so far this year nationwide, according to the Center for Responsive Politics, and its chairman, U.S. Rep. Greg Walden, R-Ore., called it “a big investment for us.”

“I think it speaks to what needs to be done to win this race, coupled with what Bruce is doing,” he said in an interview. “I think it should be adequate to put it away.”

No Republican has held the seat 2nd District seat since early 1995, and the district has gone for Democratic presidential candidates since 1992. It’s also more conservative than the rest of Maine. In 2002, when Michaud was elected, he won by just 9,000 votes against Republican Kevin Raye.

Momentum might be shifting in Republicans’ favor. The Portland Press Herald on Sunday released a poll showing Poliquin, 60, a former state treasurer from Oakland, 10 percentage points up on Cain, 34, an state senator from Orono who was ahead in a June.

Amy Cookson, a spokeswoman for Cain, declined to comment on the poll, saying the campaign believes the race to be close, which it has said all along. “Emily is having great conversations with voters across the district and on the phone,” she said.

But Republicans say it’s a sign that defending the seat will be an uphill climb for Democrats, who are expected to lose ground nationally in a midterm year for their party’s president, Barack Obama, whose approval rating is at 43 percent nationwide, according to Gallup.

Walden, speaking in Portland after attending a fundraiser with Poliquin in Bangor, called 2014 “a send-a-message election” in which voters are expressing frustration with the administration.

Over the past week, national interests have focused increasingly on Maine.

The National Republican Congressional Committee’s first ad, taking Cain to task on energy policies, began running on Tuesday. Last week, House Speaker John Boehner, R-Ohio, came to Maine for a fundraiser for Poliquin in Portland. The same day, a Democratic group announced $270,000 in ad purchases against the Republican.

The Democratic Congressional Campaign Committee hasn’t bought ad time in Maine yet, but it says it will continue to be engaged in the race.

Mark Brewer, a political science professor at the University of Maine, said the recent developments suggest that the parties see the district as increasingly competitive, perhaps because of poll data or other reports from the grass-roots level.

Walden said Poliquin is meeting national expectations so far.

“Generally speaking, if money’s coming in, that means that the race is tightening,” he said.

On Saturday, Poliquin said he’s buoyed by the support he’s seeing nationally and in the 2nd District, and expects a close race to the end, but he’s optimistic.

“We expect to win,” he said.