Don’t look now, but the race between Democratic U.S. Rep. Collin Peterson and Republican challenger Torrey Westrom has become, in one respect, one of the hottest in the country.

Outside groups have already spent $3.9 million the district, according to the Center for Responsive Politics, tenth most among House races in the U.S. this year as of Friday. The biggest players are two groups, the parties’ main House campaign committees: the National Republican Congressional Committee, which has spent $2.1 million hammering Peterson, and the Democratic Congressional Campaign Committee, which has spent $1.3 million doing the same to Westrom.

But the liberal House Majority PAC parachuted in this week with a $330,000 ad buy meant to defend Peterson, a big buy from a super PAC that’s primarily played in Minnesota’s 8^th District, and an indication that at least some other groups are considering investing in the 7^th. (A conservative group spent a bit on ads and mailers against last winter, but hasn’t been in the race since.)

“We haven’t seen the type of activity, on television certainly, before, for Peterson or against Peterson, or for his Republican opponent or against his Republican opponent, for long as I’ve been observing this race,” said two-time gubernatorial candidate Marty Seifert, a 7th District resident.

All of this in a district that Peterson has won with healthy double-digit margins in the past seven election cycles. But, after years of threatening to target Peterson — and years of easy victories for the incumbent — Republicans are finally following through, flooding the district with cash and ads, and Democrats are countering.

Operatives on both sides of the aisle, in the 7^th and nationally, agree on a handful of reasons why.

A shrinking map

Peterson’s electoral tenure has been defined by one blowout after another. Since 2002, his average margin of victory has been 31.9 percent, despite representing a district that often goes for Republican presidential candidates. Peterson’s margins have shrunk over the last few cycles, but not enough to suggest any seismic shift in support for him in his district.

Even so, the new focus on the 7^th is a matter of math more than anything else. Peterson represents a district that went for a Republican presidential candidate, Mitt Romney, by 9.7 percent in 2012. With the ranks of these split districts down to just a couple dozen, Republicans say Peterson is simply on the short list of should-be targets.

Congressional Districts highlighted in red were won by Romney in 2012 but are represented by Democrats. Districts in blue were won by Obama but are represented by Republicans.

Last year, the NRCC included Peterson in its seven-member “Red Zone” program targeting Democrats representing House districts that went for the last three Republican presidential candidates. Two of those candidates have since retired, and the NRCC is on the air against the remaining five.

Nationally, Republicans are on offense and widely expected to have a good showing on Nov. 4, maintaining or even adding to their majority in the House. Since they have less need to defend seats, they can afford to target seats like Peterson’s — Republican-leaning, but long held by Democrats.

But Republicans acknowledge that Peterson has done little on the policy-side to suddenly alienate his constituents, and Democrats aren’t ready to abandon a former committee chairman and 23-year member of their caucus. Peterson runs a bare bones political operation, and while they insist internal polling shows him well ahead, national Democratic groups are swooping in to protect him from Republican attacks.

In other words, the 7^th, on paper, should be a battleground district. Republicans are simply trying to make it one this year, and Democrats are responding in kind.

“There’s not a lot of House seats for both sides to quibble over and this is one,” Seifert said. “I think they look at it as an opportunity too good to pass up at this point.”

A stronger challenger

Sen. Torrey Westrom

Both sides acknowledge that Westrom is running a stronger campaign than those of Peterson’s past Republican rivals.

Westrom raised $430,000 through July (new fundraising reports are due next week) and the NRCC put him in their “Young Gun” program of top recruits, He’s been in the state Legislature for 18 years, and his state Senate district covers a large swath of the 7^th. Republicans say he should prove to be better known than past Republican candidates, like businessman Lee Byerg, whom the GOP twice turned to in the 7th.

“The difference is we’ve got an awesome candidate,” 7^th District state committeeman Scott Dutcher said. “A guy like Torrey can carry his message in a unique way, and in such a stronger way than an average guy.”

Republicans positively rave about Westrom, both his political skills and his personal story. Blinded in a farming accident at the age of 14, Westrom went on to become a lawyer and win a seat in the state House in 1996. He was elected to the state Senate in 2012.

“Torrey Westrom has a great story, he’s been somebody who’s gotten things done in St Paul, he’s been willing to work across party lines to get things done for his rural district,” Republican National Committeeman Chris Tiedeman, a 7^th District native, said. “He’s a very attractive candidate.”

An anti-incumbent mood

Polls tend to show anti-incumbent sentiment percolating among voters this year, but voters are notoriously fickle — they’re often in favor of replacing everyone in Congress, but not their own member when asked directly. Republicans hope their ads highlighting the perks of Peterson’s office  — mileage reimbursements for private air travel around the district, etc. — will tap into any potential anti-incumbent anger and alienate him from voters.

“Things have changed,” Tiedeman said. “People have a general frustration with Washington, period. You ask that across party lines, people have a frustration with what’s happening in Washington, and I think Collin Peterson has become Washington.”

Democrats say that argument won’t work against Peterson, who excels at retail politicking and connecting with the biggest interests in his district, especially agriculture. He’s also one of the last remaining conservative “Blue Dog” Democrats in the House, and he’s easily survived Republican waves in the past because, Democrats say, his views align with his constituents. They point out that he’s earned endorsements from traditionally conservative sources like the National Rifle Association and the Minnesota Farm Bureau.

“I think [the ads are] kind of ridiculous, but that doesn’t mean that some people won’t listen to them,” 7^th District DFL chair Nancy Larson said. “We’ve had Collin here for years he’s been known as being frugal, for being bipartisan, for being a Blue Dog, for being one of the last people you’d expect to misuse anything.”

A look toward 2016?

For their part, Democrats contend Republicans are simply looking toward the 70-year-old Peterson’s eventual retirement, setting up a candidate like Westrom to step in in Peterson’s wake to take and hold the district for the GOP.

Republicans argue they wouldn’t be spending millions of dollars in the district if they didn’t think they had a chance to win the seat this year. Peterson somewhat famously delays his re-election plans until the year of the election itself — we didn’t know until March that he would run this year — so he hasn’t made any decisions about his future yet. But Larson said both sides are preparing for the day he calls it quits, and that’s manifesting itself in Republicans’ spending spree this year.

“They’re trying to get their bases going and interested in trying to pull in new people,” she said.  “At some point, we don’t know when, Collin will retire, and you’ve got to be ready.”

Devin Henry can be reached at dhenry@minnpost.com. Follow him on Twitter: @dhenry