President Trump on Friday declared his support for Republican candidates in Tennessee, Michigan and Ohio, wading into a pair of races in Midwestern states he won in 2016 and a conservative state in which he remains popular. 

Trump also said he would ramp up his campaigning for House and Senate Republicans in the coming weeks, noting he has asked White House chief of staff John F. Kelly and other aides to draft a list of the 25 most competitive congressional races so he can get more involved.

“I am going to work very hard,” Trump said of his political activity during an interview with conservative media personality Sean Hannity. “I’ll go six or seven days a week when we’re 60 days out. I will be campaigning for all these great people that do have a difficult race and we think we’re going to bring them over the line.”

In a morning tweet, Trump threw his weight behind Iraq War veteran John James, who is vying against businessman Sandy Pensler for the Republican nomination in Michigan’s U.S. Senate race. The primary is Aug. 7.

“.@JohnJamesMI, who is running in the Republican Primary in the great state of Michigan, is SPECTACULAR!” Trump said. “Rarely have I seen a candidate with such great potential.”

He hailed James as a “West Point graduate, successful businessman and a African American leader” and said he “is strong on crime and borders, loves our Military, our Vets and our Second Amendment.”

An NBC News/Marist poll conducted this month showed James leading Pensler 30 percent to 23 percent among likely Republican primary voters. With 46 percent of likely GOP voters remaining undecided, however, Trump’s endorsement could be a deciding factor in the race.

The winner of the Republican primary will face Sen. Debbie Stabenow, D, whom polls show leading both of her potential general election opponents by double digits.

In Ohio, Trump is endorsing Troy Balderson, the Republican nominee in the Aug. 7 special election to fill the remaining months of the term of Rep. Patrick J. Tiberi (R).

In a tweet, Trump said the race in Ohio’s 12th Congressional District is “so important to the Republican Party.”

“Cast you early vote or vote on August 7th,” Trump said. “Troy is strong on crime and borders, loves our Military, our Vets and our Second Amendment. He has my full and total Endorsement!”

Balderson is facing Democrat Danny O’Connor in the race. Trump won the district by more than 11 percentage points in 2016, but Democrats are hoping that O’Connor’s moderate profile will help draw voters to their side.

And in Tennessee, Trump tweeted his endorsement of Rep. David Kustoff, a freshman House Republican who is facing a primary challenge from radiologist George Flinn, a wealthy candidate funding his race. 

“Congressman David Kustoff has been a champion for the Trump Agenda — I greatly appreciate his support,” Trump tweeted. “David is strong on crime and borders, loves our Military, Vets and Second Amendment. Get out and vote for David on Thursday, August 2nd. He has my full and total Endorsement!”

Seung Min Kim contributed to this report.