President Donald Trump speaks during a 'Make America Great Again' rally at Landers Center in Southaven, Mississippi, on October 2, 2018. Mandel Ngan | AFP | Getty Images

President Donald Trump is swooping into Midwestern states to try to boost House Republican candidates hurt in part by his own trade policy. He has a new tool to limit the political damage. The president started a swing through key midterm states Thursday in Minnesota, which he will follow with rallies in Kansas on Saturday and Iowa on Tuesday. Facing backlash to his tariffs that brought targeted retaliation against farmers, Trump is touting the deal his administration struck this week to tweak, but largely keep intact, the North American Free Trade Agreement. "NAFTA has been one of the great disasters of all time and now we have a great and fair deal. We have a fair deal," he said Thursday night in Rochester, Minnesota, within the state's battleground 1st Congressional District. The area has a strong agricultural presence, and the state overall plays host to four competitive House races in November as Republicans and Democrats battle for control of the chamber.

As the president slapped tariffs on key trading partners and threatened to scrap NAFTA this year, candidates in key races in Minnesota, Iowa and Kansas largely criticized the duties and defended the three-nation trade agreement. Securing a revised trade deal could reduce uncertainty for farmers and manufacturers as Trump's poor approval rating and protectionist policies threaten to help Democrats pick off multiple GOP-held House seats. The results hold huge stakes for Trump personally: a Democratic House would not only fight his policy goals, but also it would likely push to release his tax returns or launch more investigations into his administration. Jim Hagedorn, a Republican who has opposed tariffs as he tries to win the Democratic-held 1st District, cheered the trade deal revision. It "will provide enhanced trade opportunities for our farmers and manufacturers," said Gregg Peppin, a spokesman for Hagedorn. He is running against Democrat Dan Feehan, who has said the district's farmers are "suffering sizable losses" because of a "reckless trade war." Feehan's campaign did not respond to CNBC's request for comment. Feehan tweet Nonpartisan election analysts consider the contest to replace retiring Democratic Rep. Tim Walz a toss-up. The seat stretches from Minnesota's western to eastern border at the southern edge of the state. While Trump can call the deal he dubbed the United States-Mexico-Canada Agreement a win, he still has one glaring trade problem: China. An escalating series of tariffs leveled by Washington and Beijing led to duties on American agricultural exports such as soybeans and pork.