All eyes are on Sen. Chuck Grassley of Iowa as the Republican Party aims to win back the Senate majority in 2022.

One of the biggest questions hovering next year's midterms is whether the 87-year-old Grassley will run for an eighth six-year term in the Senate.

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The senator is remaining mum.

"I'll be making that decision sometime this fall," he has repeatedly said so far this year as he points to an announcement sometime likely in October or November.

Sen. Chuck Grassley, R-Iowa, listens during a hearing of the Senate Judiciary Subcommittee on Privacy, Technology, and the Law, on Capitol Hill, Tuesday, April 27, 2021, in Washington. (Al Drago/Pool via AP) (Al Drago/Pool via AP)

The Senate 2022 map shows why Grassley's eventual decision is so important.

The chamber is split 50-50 between the two parties, but the Democrats hold a razor-thin majority due to the tie-breaking vote of Vice President Kamala Harris, who serves as president of the Senate. That means the GOP only needs a one-seat pickup to regain the majority.

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Republicans are defending 20 of the 34 seats up for grabs in 2022, including five open seats that are held by GOP senators retiring next year. Two of those retirements are in the battlegrounds of North Carolina and Pennsylvania. The GOP is also defending open seats in the safer but potentially competitive states of Ohio and Missouri, and in red Alabama.

But Republicans see pickup opportunities in the key battlegrounds of Georgia and Arizona, where Democrats Raphael Warnock and Mark Kelly last cycle won special elections to serve two years in the Senate and are up for reelection in 2022. The GOP also sees possible pickups in Nevada and New Hampshire, where first-term Democratic Sens. Catherine Cortez Masto and Maggie Hassan are running for reelection.

Which is why the decision by Grassley – who won reelection in 2016 by nearly 25 points – is so important.

"It's clear that he guarantees he hold that seat without much work or money," a Republican operative who works on Senate races told Fox News. "If he doesn't run, there's a chance we'll have to spend some money there."

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The operative, who asked to remain anonymous to speak more freely, stressed that "Grassley understands the dynamic that if he runs, he wins. He doesn't need people to tell him that."

A GOP strategist and veteran of Senate races emphasized that "Chuck Grassley is the difference between a race that is an afterthought in the broader landscape of the Senate map and one that becomes another opportunity for Democrats to try and pick up a seat."

Pointing to then-President Trump's eight-point victory over now-President Biden in Iowa in November and GOP Sen. Joni Ernst's reelection over Democratic challenger Theresa Greenfield by nearly seven points, the strategist noted that "regardless of what happens with Chuck Grassley, Republicans certainly start off with an advantage. But it is sleepy unless Chuck Grassley decides to retire."

And Senate Minority Whip John Thune of South Dakota, the number-two Republican in the chamber, told Politico in a story published Monday that Grassley is "the best path we have to keep the seat in Republican hands and take it off the map."

Sen. Rick Scott of Florida, who chairs the National Republican Senatorial Committee, which is the Senate GOP's reelection arm, told Fox News in January that he was "optimistic" that Grassley would seek reelection in 2022. And on the eve of an April trip to Iowa, Scott told the Des Moines Register he was "very optimistic that Sen. Grassley's going to run … Actually, I'd be surprised if he doesn't."

Grassley's age continues to be a factor. While an octogenarian, Grassley remains sharp both mentally and physically.

"Look, the guy can outthink me, outwork me and outrun me, literally. I'm sure that he can be a United States Senator for six years," Iowa GOP chair Jeff Kaufmann said earlier this year on "Iowa Press" on Iowa PBS.

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Just 28% of Iowa adults said they hoped Grassley would run for reelection in 2022, according to at Des Moines Register/Mediacom Iowa Poll released in March. And the senator’s job approval and favorability ratings dipped to their lowest levels in nearly four decades.

But Grassley brushed off the survey, telling reporters at the time that "one poll doesn't make much of a difference. I don't pay attention to polls all that much."