Minnesota's Second Congressional District is just the kind of politically swinging, suburban-to-exurban turf that's become the hottest campaign battleground of the Trump era.

A mix of major suburbs like Lakeville and Eagan, small regional cities like Red Wing and Northfield, and rural areas south of the Twin Cities, the Second was a Republican stronghold for the 14 years that it was represented by former Rep. John Kline. Former Rep. Jason Lewis kept it in GOP hands in 2016, the same year President Donald Trump narrowly carried the district.

Two years later, DFL Rep. Angie Craig ousted Lewis — one race in a nationwide suburban bloodbath for Republicans that was interpreted as a sign of Trump's waning popularity with college-educated white voters.

Minnesota Republicans took their time to find a challenger for Craig, and the election handicappers at the Cook Political Report give the seat a "Lean Democratic" rating.

But Republican operatives have been trying to create buzz for Tyler Kistner, who helped his own cause last week when he announced a second-quarter fundraising total that surpassed Craig.

The incumbent took in a little more than $725,000 in April, May and June, to $744,000 for Kistner. It's a small difference but important symbolically for Kistner. Republicans won't come close to regaining a House majority without winning back some suburban seats this year, and good fundraising tends to beget more good fundraising.

Craig still holds a big cash-on-hand advantage, $2.5 million to Kistner's $511,000. But that didn't stop her campaign from raising an alarm bell in a new plea to donors: "Look, we told you the GOP would do everything in its power to flip this seat. And now, we learned that our opponent has outraised us."

(I love that hint of guilt: "Look, we told you …")

Craig has taken what you could call a workhorse approach to re-election: introducing lots of bills (she passed two into law, putting her at the top of the five new members of the Minnesota delegation); working hard on accessibility and visibility in the district; and emphasizing bipartisanship and problem-solving.

"Send in the Marine," goes Kistner's frequently tweeted campaign slogan. Kistner's fundraising news release was emblazoned with an image of him in military dress. (He's recently retired from the Marines.) The news release included the Department of Defense-required disclaimer that the U.S. military does not back political candidates.

The Defense guidelines state that "members not on active duty" … "may NOT, in campaign literature" … "Use or allow the use of photographs, drawings, and other similar media formats of themselves in uniform as the primary graphic representation in any campaign media, such as a billboard, brochure, flyer, Web site, or television commercial."

I asked the Kistner campaign about the use of his uniform.

"We believe we have followed the DOD guidelines to the spirit of the law, but out of an abundance of caution we will be changing the header," said Billy Grant, Kistner's chief strategist.