It would be easy to label the speech, as well as his vote nine days later to reopen the government without funding for Trump's wall, as signs Isakson had lost patience with Capitol Hill's escalating brinkmanship and constant gridlock.

Indeed, the typically genteel and soft-spoken lawmaker has had several recent moments of public exasperation — including an impassioned floor speech in which he took a shot at the president for sullying the memory of Sen. John McCain and even questioned his own actions to join the Georgia Air National Guard rather than going to Vietnam.

But Isakson and his top aides and allies dispute the notion the veteran deal-maker is becoming disenchanted with Washington or Trump. Instead, they say some of his more incandescent moments are intentional, a technique to break through the noise and advance his goals.

“I subscribe to the theory that the weight of my words is directly proportional to how few I use, so I don’t speak unless I’ve got something to say,” Isakson said in a recent interview in his Capitol Hill office, which includes a custom-built case filled with coins from local military bases, footballs from various Georgia universities and other mementos from more than 40 years in public life.

Now in his 21st year on Capitol Hill, Isakson faces the ultimate gut check as the Senate takes up a Democratic resolution to nullify Trump’s border emergency. The vote will pit some of Isakson’s core principles against one another: his deep loyalty to his party, his working relationship with Trump — and Democrats — as well as his conservative wariness of executive overreach.

The art of the deal

From the outside, Isakson seems out of place in today’s Washington.

A party man with a deal-making streak, Isakson is serving under a dogma-shattering president whose larger-than-life personality and burn-it-down negotiating style have seemingly left little room for lawmakers such as Isakson. This holds particularly true on immigration, an issue that Isakson long has tried to tackle.

Policy decisions are increasingly made in the office suites of party leaders, not among congressional committees. And with the day’s biggest issues so politically weaponized, lawmakers have less incentive to seek out bipartisan solutions if it will harm their chances of re-election.

Still, Isakson has found a way to operate in the cracks.

On the Veterans Affairs Committee he heads as chairman, he's quietly quarterbacked significant bipartisan compromises on bureaucratic accountability issues and private health care options following the Department of Veterans Affairs' wait times scandal.

And he's developed a reputation as a go-to when Democrats need bipartisan coalitions. President Barack Obama reached out to Isakson and his then-Senate colleague Saxby Chambliss to build momentum for a comprehensive immigration policy overhaul in 2013. And before a series of surgeries, Isakson was a popular travel buddy for Democratic lawmakers on fact-finding trips abroad.

At times those trips raised eyebrows, even among his own staff — such as when the Republican traveled to Greenland with one of the Senate's most prominent liberals to learn about climate change — but they helped build relationships that would pay political dividends, as when that same Democrat helped Isakson during a high-stakes water wars fight in 2013.

Isakson’s years-long battle with Parkinson’s disease has slowed him down physically — he uses a cane and has a shuffling gait — but he’s continued to position himself at the center of Capitol Hill’s biggest debates.

A Realtor before he entered politics, Isakson built an empire by getting buyers and sellers to the negotiating table, a skill set that’s transferred into his D.C. day job.

He first flirted with politics as a student at the University of Georgia, volunteering for Republican Barry Goldwater’s presidential campaign in 1964. But he didn’t formally dive into GOP politics until he was in his late 20s.

“I went and looked at the vote patterns and where I lived, which is east Cobb County. (It) had gone Republican, but nobody else had around them. It wasn’t a total Republican district, but it looked like it was moving that way, so I said, ‘Well, I really believe more in what Richard Nixon stands for economically than George McGovern,’ ” Isakson recounted.

Being a Republican in those days was a rarity in Georgia. When he took over as state House minority leader in 1983, there were only 24 GOP lawmakers to Democrats’ 156 members.

“I mean, that’s the Alamo,” said Heath Garrett, Isakson’s longtime political strategist. “He had to figure out how to get a few things done and how to work with the opposition. … He picked his battles, but he found ways to start and implement different policies. But he learned how to do it with people who didn’t agree with him.”

Back then Democrats didn't have to consult the GOP to get most legislation through the Statehouse. But state Rep. Calvin Smyre, D-Columbus, who served as floor leader for Gov. Joe Frank Harris when Isakson was minority leader, said the Republican became a key player on issues where there was a rural-urban split within the Democratic Party, as when the Georgia Dome and Georgia World Congress Center were being developed.

Smyre said Isakson stuck out to him.

“He was very amicable and approachable,” said Smyre, who’s still serving in the Legislature. “He’s been the same to me whether or not he was in power or out of power, and I think that’s key when you’re consistent with how you carry yourself.”

For the press, however, trying to track Isakson during a high-stakes negotiation can be a challenge.

He dodges the spotlight to create space to operate. And he’s often cryptic about his position so he’s not later pinned down.

"I'm not wiling to say what I will or won't accept, except to say I'm willing to consider whatever we need to do to get this problem off the table and in the communities of our country," Isakson told The Atlanta Journal-Constitution as a round of immigration talks heated up in the fall of 2017.

The loyalist

Despite his deal-making reputation, Isakson is no centrist.

His stint in the Statehouse made him a godfather of the modern Georgia GOP, and he’s largely aligned with the party’s business-friendly wing.

But his proclivity to cut deals has won him criticism from both sides of the aisle. Some conservatives have pinned him with the pejorative RINO label — "Republican in name only" — for cutting deals with Democrats and backing large spending packages that have added to the national debt.

“Personally, he’s a very nice man, but his votes in recent history have just not inspired the people who are in the base of the Republican Party,” said Alex Johnson, a DeKalb County attorney who leads the Georgia Republican Assembly, a conservative political group. “Republicans need to watch the pocketbook to make sure that we don’t start getting obligations that we can’t fulfill in order to win elections. … I would say that Isakson and 90 percent-plus of the people of Washington have lost sight of that.”

And he’s a frequent target of criticism from the left for casting votes in favor of many of Trump’s policies.

He has voted with the president’s priorities more than 91 percent of the time, according to the political blog FiveThirtyEight.

Isakson's allies say he's been able to weather criticism because of his accessibility and constituent service work. He won over 18 percent of black voters in the 2016 election, according to one exit poll, when only 9 percent went for Trump, and 12 percent of Democrats, compared with Trump's 5 percent.

On Capitol Hill, Isakson is firmly aligned with his friend Mitch McConnell. When the Senate is in session, Isakson is known as a regular, sometimes unannounced visitor in the majority leader’s office, where he cracks jokes and chats up staff about the floor schedule. He’s served as McConnell’s emissary on the Ethics Committee for more than 10 years, a thankless job that most lawmakers look to avoid.

“I couldn’t have a higher regard for anybody than I do Senator Isakson,” McConnell told the AJC in an interview. “I know he’s level-headed, has good judgment, is not going to go after somebody who doesn’t deserve to be gone after, whether they’re a Democrat or Republican,” on the Ethics Committee.

While Isakson rarely breaks with the party on major legislation, he’s become more of a free agent when it comes to the president.

Isakson endorsed Trump ahead of the 2016 Republican convention, and he has worked closely with the White House on veterans legislation and executive branch nominees. But he's declined to defend many of the president's more incendiary statements and policy proposals, and he has pointedly criticized Trump's actions at moments such as the Charlottesville march, his behavior toward McCain and his "shithole countries" comment.

Trump's increasing reliance on executive actions has also put Isakson in a quandary, since he at times criticized Obama for overreaching. Perhaps the biggest test of his support will be in the weeks ahead, when he'll have to take a position on the president's emergency declaration on the southern border.

Isakson, in characteristic fashion, has not said where he stands. He has expressed wariness about giving any individual too much unchecked power, but he's also raised questions about Democrats playing politics.

“I want to make sure we understand whatever we do is going to apply to both parties — or no party — and anybody who gets elected president is going to have the authority to declare the emergency. And it’s going to set a precedent in terms of what that emergency might be,” Isakson told the AJC. “Because of that, we have to be very careful.”

Isakson's vote could test the political capital he's built in the Senate over the past 14 years. Democrats whom he's worked to build bridges with over the years will be pressing him to buck his party. There are the Georgia military bases that could lose construction money under a national emergency. And then there's McConnell, for whom he's been a loyal friend and foot soldier.

That capital bought Isakson the room to take a stance during the shutdown, when, infuriated by a standstill in negotiations, he informed McConnell and Vice President Mike Pence that he would be supporting a Democratic bill to reopen the government that didn’t include wall funding. (But first, Isakson backed a White House-endorsed measure that also set aside $5.7 billion for Trump’s wall.) His defection, along with that of a handful of other Republicans, helped set the table to end the shutdown.

Isakson said he sees his role in Washington evolving as he climbs to the top of the seniority ladder and several of his more deal-minded peers are retiring.

“I’m now the 25th in seniority in the Senate. There are 75 people in the Senate that haven’t been there as long as I have,” he said. “So when I say something, I want to sound like I’m 25th in seniority and not blow that advantage.”

Isakson has much more room to do it than some of his colleagues given the relationships he’s built after decades in politics. It also helps that he’s not up for re-election until 2022.

During the shutdown, Isakson “was just looking for the right leadership,” said Chambliss, a longtime friend stretching back to their days at UGA. “He actually sort of found it (within) himself.”

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