SIOUX CENTER, Iowa (AP) — In dress shirts and pants, Chuck Grassley and Tom Cotton dropped to their knees on stage at a recent Iowa Republican Party fundraiser and began pumping out pushups. The 87-year-old Iowa senator's were slow and deliberate while his Arkansas colleague's were crisp and level, befitting the 44-year-old former Army captain.

The 22 reps were part of a campaign to curb veteran suicides. But for Grassley, a senator considering a bid for an eighth term, it was also a moment to send another message to voters: I can still keep up.

After 40 years in the Senate, serving under seven presidents, Grassley's resilience isn't just physical. Once proudly bipartisan, Grassley adapted deftly to the new hyperpartisanship of the Trump era. While some of his fellow longtimers in Washington are calling it quits, fed up with the rightward lurch of the GOP or the inertia in Congress, Grassley has set out to show he's thriving.

“He goes out and talks to Republicans, and sees the party still includes a number of people who are big-time Trump supporters," said longtime adviser Mike Schreurs. “One way or another, you've got to accommodate them. And that's Grassley's astute politics.”

Grassley has said he will announce his plans this fall, later than usual for the senator, who typically has decided to run again immediately after each of his previous reelections.

But the senator's campaign team is functioning as if he’s running. Grassley and his pollster Brian Tringali met last month with leaders of the National Republican Senatorial Committee at their headquarters in Washington. Other advisers, including Grassley’s longtime advertising consultant Fred Davis, participated in the meeting via Zoom. They reviewed Grassley's polling and fundraising head start, pleased with what they saw.

The senator is raising money at a healthy clip. He reported having $2 million in his campaign account at the end of the first quarter. It's been enough to scare off any big-name challengers. Two little-known western Iowa prospects have announced their candidacy: Republican state Sen. Jim Carlin and Democratic farmer Dave Muhlbauer.

Still, Grassley's age — he would be 95 at the end of his term if he won — inevitably raises questions about his future, and the senator isn't shying from them. Advisers say Grassley has said he wants to avoid a situation like the final months in office of Sens. Robert Byrd, a West Virginia Democrat, and Strom Thurmond, a South Carolina Republican.

Byrd was in and out of the hospital before he died in office at age 92 in 2010. Thurmond, frail and guided through the Capitol in a wheelchair before retiring in 2003, died six months later at age 100.

Grassley would be the second-oldest member of the Senate and among the 10 oldest senators in history.

With his signature gruffness, Grassley acknowledges his age is “one of the reasons that I’ve put off making the decision until later on.”

“Who knows? I could die tomorrow,” he told The Associated Press as he visited tiny Ida Grove in northwest Iowa last week. “If I announce I’m running, I’m planning on living to be 95. But I might not live that long.”

His health habits suggest otherwise. The pushups aren't just for show, but part of his daily routine, he says. He also runs 12 miles (19 kilometers) per week, though he chuckles calling it “a shuffle.” He wakes up at 4 a.m. and is in his Washington office by 6 a.m.

Despite the pace, and his activity on Twitter, there's no hiding Grassley has decades on most of his voters.

At events, Grassley references his hearing aid, sometimes as a joke, but he also relies on a staffer to repeat what he misses. He often illustrates his points with creaky references and examples that predate his listeners.

Meeting with a group of young professionals in Sioux City last week, Grassley fielded a question about same-sex marriage by noting that it reminded him of some constitutional research he did in college in 1953.

When answering a question about the fuel tax and electric cars, he illustrated the improvement in fuel efficiency over time by recalling a billboard from the 1950s advertising a Chevrolet that got up to 15 miles (24 kilometers) per gallon.

“He referenced things long in the past," said Josiah Paulsrud, 35, of Sioux City, who is a Republican and undecided about Grassley. “Whether it was him trying to educate people or rambling on, I can't say.”

Five Senate Republicans, including Richard Shelby of Alabama, who is also 87, are retiring after 2022. In announcing his retirement, two-term Republican Sen. Rob Portman of Ohio expressed frustration with the dysfunction in Washington.

Grassley, however, has adapted smoothly to changes in the party. He's consistently supported Donald Trump's agenda and often his political tactics. At times, he's even taken a lead role in satisfying the party's vocal right wing.

Grassley helped spur Trump Supreme Court nominee Amy Coney Barrett's confirmation days before the 2020 election — even after effectively killing Democratic President Barack Obama's nomination of Merrick Garland, saying it came too close to the 2016 election.

He partnered with the pro-Trump Wisconsin Sen. Ron Johnson on a high priority for the far right, investigating Hunter Biden's financial dealings last year as his father ran for president.

And, having criticized him as president, he has been nearly silent on Trump's false claims that he won the 2020 presidential election.

When pressed at a recent public meeting to call out Trump's falsehood, Grassley declined.

Grassley replied curtly to retired anesthesiologist Phil Dokter: “On December the 12th, after the electoral votes were cast, Biden is the president of the United States.”

“That’s not enough. You’ve used your soapbox over the decades," said Dokter, an independent who has voted for Grassley in the past. “And we’re talking about a big deal here.”

Grassley moved on to the next question.

But the senator hasn't always been a Trump acolyte. He voted to count Arizona’s and Pennsylvania’s Electoral College votes the day of the deadly Capitol riot in January. He also objected loudly to waivers the Trump administration gave petroleum companies from the federal Renewable Fuel Standard, a goal that helps Iowa farmers.

The senator says he's doesn't consider Trump the de facto leader of the national Republican Party, despite the former president's continued effort to influence Republican primary contests.

“Right now, the Republican Party doesn’t have a leader. We’ve got people who have great influence within the party like Sen. Cotton, Sen. (Ted) Cruz, Sen. Lindsey Graham. People like that," he said in the AP interview. “And Trump is one of them."

Still, Grassley's appeals to the right appear to have hurt his approval in Iowa, once called “stratospheric" by J. Ann Selzer, director of The Des Moines Register's Iowa Poll.

In June, the poll showed Grassley's approval at 45%, down 30 percentage points from 2009, when he was a key figure in bipartisan negotiations over health care legislation.

His approval remains healthy among Republicans, and more Iowans approve than disapprove of his performance. Grassley's numbers have dropped sharply among Democrats and fallen among independents, both of whom used to pad his high ratings.

“Democrats are no longer willing to give him the benefit," Selzer said. “But it could also be that he’s doing things, more things, that are ticking off Democrats. The two are conjoined."

Grassley won't need the Democratic support to win. Iowa has drifted decidedly Republican in the past decade, electing and reelecting GOP governors, filling longtime liberal Democratic Sen. Tom Harkin's seat with conservative Republican Joni Ernst.

The state voted twice for Trump, a fact that appeared top of mind as Grassley visited a friendly crowd in Ida Grove. The senator railed against the Biden administration's U.S.-Mexico border policy, and when asked his opinion about Trump's recent visit to the border, Grassley gave the audience of 50 in the town's recreation center what they wanted.

“Nobody can tell him what to do," he said. “And if you did tell him what to do, he wouldn’t do it anyway."

The gym burst into applause and laughter.