Republicans are excited to welcome their standard-bearer, President Donald Trump, to Minneapolis on Oct. 10. Senate Majority Leader Paul Gazelka, a Nisswa Republican, chimed in: "I said that Trump is going to go after Minnesota, and a rally in October is more evidence it's true. Go Trump!"

Presidential visits tend to generate lots of press, most of it positive. They create enthusiasm among ardent supporters, keeping them energized.

These visits also offer a chance for campaigns to collect names and e-mail addresses of potential volunteers. The events require organization that is a good dry run for the election season to come. And, they are usually accompanied by a fundraiser, providing cash that might flow back to the home team.

Trump came to Minnesota for two big rallies in 2018, one in Rochester and another in Duluth. Republicans flipped both congressional districts from blue to red.

So, you would think the data would be clear on the impact of presidential visits. But it's not. A 2016 article in the Annals of the American Academy of Political and Social Science found that "visits themselves have little effect on local media markets." Evidence from the closing stages of the 2012 campaign indicated that "respondents … have little knowledge about candidate visits, and the visits themselves have only a small and evanescent effect on voter intentions."

Trump disagrees, and is said to believe that one more visit to Minnesota would have clinched the state for him in 2016.

Much is unknown about this visit. Unlike his visits to Rochester and Duluth, this time Trump is traveling to the heart of "the resistance" in downtown Minneapolis. And it's just a short ride to Little Mogadishu, the heart of the Somali-American community whose migration to Minnesota was referred to by Trump in 2016 as a "disaster."

The downside of the visit for Republicans, a GOP operative told me last week, is that it will also energize the DFL. Demonstrators will come out in big numbers, confronting Trump rallygoers in a scene that could quickly change the image of "Minnesota Nice" into something fiercer.

Like I said: Much is unknown.

We don't have a lot of polling, but Morning Consult polls monthly and Trump is underwater, with 41% of Minnesotans approving of his job performance and 55% disapproving. He's been hovering in the same place since spring 2017. On the other hand, Jennifer Duffy, a senior editor of the Cook Political Report, is skeptical of polls these days, and it's her job to study them all day. "The response rates are in the single digits. And they're doing them on the cheap," she told me.

But we can use the 2018 election as a proxy. The DFL won a crushing victory, capturing all the statewide races and taking the majority in the Minnesota House.

Can Trump make the significant gains he would need to win here? He doesn't have to. He just needs to drive up the negative perceptions of his opponent, maybe flip some late-deciding swing voters. It was a formula that came within 44,000 votes in 2016.

J. Patrick Coolican 651-925-5042 Twitter: @jpcoolican