Long-shot Republican presidential candidate Perry Johnson isn't ruling out a run for the open Senate seat in battleground Michigan.

"Obviously, it’s no secret that I’ve had a lot of calls to run for this seat because they do want to win this seat. But at this point in time, my focus is right on the presidential [race], and, believe me, that’s taking all my time and energy at this point," Johnson said Thursday in a Fox News Digital interview.

The Michigan businessman and quality control industry expert failed to qualify for the first two Republican presidential nomination debates, including Wednesday's second showdown, a FOX Business co-hosted event at the Ronald Reagan Presidential Library in Simi Valley, California.

Johnson now faces an even steeper climb to make the stage at the third showdown in early November in Miami, Florida, because the Republican National Committee continues to raise polling and donor thresholds the candidates need to reach to qualify for the upcoming debates.

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Pointing to the polling threshold for the third GOP debate, Johnson said "4% is a big bar."

"When you’re an outsider, it’s very hard to get on the debate stage because, not only do you have to hit the poll numbers, then you have to have them [the RNC] say these polls are OK." He criticized the national party committee for not recognizing certain polls that don't meet its standards.

Johnson emphasized that, when it comes to his White House campaign, "right now, I think the plan is to go all in, in an individual state. If you’re not on the debate stage, that has to be the approach you take. …. The issue is to get to 4% nationally. 

"You can really only focus on one thing at a time, and when you’re running for president, it’s a full time for job."

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Johnson ran last year for the 2022 GOP gubernatorial nomination in Michigan and was considered a top contender before he and four other Republican hopefuls were disqualified because of invalid signatures. He has poured millions of his own money into his 2024 presidential campaign.

As Republicans aim to win back the Senate majority in 2024, they're eyeing Michigan, where longtime Democratic Sen. Debbie Stabenow is retiring rather than seeking another term.

"As you can imagine, I get inundated with calls because of the fact that Michigan has an open seat," Johnson said. "It’s literally a seat that Republicans have not had in Michigan in a long time."

Former longtime Rep. Mike Rogers of Michigan, who served as House Intelligence Committee chair during his last four years in office, launched a GOP Senate campaign earlier this month. Former Rep. Peter Meijer, who backed the impeachment of President Donald Trump, has formed an exploratory committee.

And Michigan State Board of Education member Nikki Snyder, businessperson Michael Hoover and attorney Alexandria Taylor have filed to run for the GOP Senate nomination.

Rep. Elissa Slotkin is the front-runner for the Democratic Senate nomination in a field that also includes actor and businessman Hill Harper, state Board of Education President Pamela Pugh and former state Rep. Leslie Love. 

Get the latest updates from the 2024 campaign trail, exclusive interviews and more at our Fox News Digital election hub.