We will get to Johnny Isakson, Jim Barksdale, Allen Buckley and Georgia's three-way race for the U.S. Senate. But first we have to strap on the hip-waders and plow through the swampy backstory:

Simply to catalog Donald Trump’s missteps in the last few days would require a librarian with sharp Dewey decimal skills. A banished baby, loose Ukrainian talk, warnings of “rigged” November elections and tin-eared gibberish about Purple Heart medals are just the beginning of a long list.

But if ranked in order of pure political damage, there is no contest.

The Republican presidential nominee’s refusal early last week to endorse the re-election of the U.S. House speaker, the highest-ranking member of the GOP in Washington, and two essential members of the Republican-controlled Senate, threatens deep damage to the party’s November fortunes.

How serious was this blunder? At a rally in Green Bay, Wisc., late Friday, the man who never reverses course, reversed course. He endorsed not just Ryan, but U.S. Sens. John McCain of Arizona and Kelly Ayotte. Trump couldn't afford to do otherwise.

Since he became the presumptive nominee this spring, Trump and the Republican leaders who control one-third of the D.C. machinery have been operating under the unspoken auspices of a mutual preservation pact.

GOP leaders have understood that abandoning Trump could cost them control of the Senate, and could even make things close in the House. Trump has at least pretended to understand that his media-driven campaign will ultimately need a 50-state ground game that only congressional networks can provide in the 90-day footrace that remains.

By snubbing Ryan, by holding himself apart from McCain and Ayotte of New Hampshire – vital seats if the GOP is to maintain its hold on the Senate – Trump has shown himself to be, at minimum, an unreliable partner.

Ryan’s primary in Wisconsin is Tuesday. The House speaker is likely to prevail over the tattooed motorcyclist who has been the recipient of  praise from Trump (and Sarah Palin).

McCain’s primary is Aug. 30. His contest is decidedly more iffy.

McCain didn’t withdraw his endorsement of Trump, even while he criticized his presidential candidate for engaging a Gold Star family in an insulting feud. McCain made his endorsement of Trump in spite of last year’s insult, in which the New York businessman said the former Vietnam POW was something other than a hero — because he was captured and spent years in a bamboo cage.

If McCain should lose his re-election bid at the end of this month, Donald Trump is likely to receive much of the blame, especially if the blame is doled out by his Senate colleagues — who, ironically, had shunned Sen. Ted Cruz of Texas precisely because he wasn’t “a team player.”

In that case, the Trump-Congress partnership might very well be over. GOP senators would become, in essence, freelancers — each trying to figure out for himself or herself what it means to be Republican. Because no one knows for sure any more.

That’s the swamp. Which we now leave for more solid Georgia ground.

A new Atlanta Journal-Constitution poll of Georgia voters shows Democrat Hillary Clinton (43 percent) with a slim lead over Trump (39 percent) in the presidential contest. More importantly, the survey shows Libertarian Gary Johnson (12 percent) having a substantial impact, especially on Republican voters.

The AJC also polled the Senate race in Georgia. In a one-on-one contest, Republican incumbent Johnny Isakson leads Democrat Jim Barksdale, 48 to 42 percent. But a third candidate, Libertarian Allen Buckley, is also in the race. In 2008, Buckley forced a runoff between U.S. Sen. Saxby Chambliss and Democrat Jim Martin.

Logic tells Buckley that he should be outpolling Johnson, his fellow Libertarian. “I’ve been on the ballot in Georgia much more than he has,” Buckley said Friday.

If the presidential and U.S. Senate contests in Georgia possess similar dynamics, Isakson, whose public career began in the state Capitol 40 years ago, could be in danger of falling into a runoff.

Which is why the Barksdale campaign has become very attached to the phrase "single digits" when describing recent Senate polls, and has begun prodding Isakson for vulnerabilities. This week, it was the Republican incumbent's attendance records on a pair of Senate committees.

Heath Garrett, the top strategist for the Isakson campaign, as much as conceded the possibility of a Thanksgiving season runoff.

“The Isakson team has been preparing for the most volatile presidential election cycle in modern history. That means anything can happen,” Garrett said.

To avoid those grueling extra innings, which would receive national attention if control of the Senate were at stake, Isakson must first be careful not to tick off Trump supporters who continue to hold sway within the Georgia GOP.

Last week, Isakson was quizzed about his endorsement of Trump. “I think it’s important to be for your ticket. If you’re an elected Republican, I think you have an obligation to be for your ticket,” Isakson told the Marietta Daily Journal. “That doesn’t mean you’re blindly for your ticket, but it means you’re supportive of your ticket and you’re supportive of your party.”

Needle-threading was required, because Donald Trump can win Georgia’s 16 electoral votes without reaching the 50 percent mark. A plurality will do.

To escape a runoff, Isakson must push beyond the 50 percent mark. He needs to attract voters, Republican, Democrat or independent, who won’t vote for Trump in November.

And now you’re privy to why we suddenly know that former Gov. Roy Barnes and his wife have maxed out their checkbooks to Isakson, a fellow Cobb Countian. Why former U.S. Sen. Sam Nunn, another Democrat, has invested $500 in Isakson. Why U.S. Rep. David Scott, D-Atlanta, has endorsed Isakson.

“Johnny Isakson is building a coalition to avoid a runoff that includes Republicans, Libertarians and Reagan Democrats,” Garrett said. “It’s almost like what Republicans had to do to win in Georgia in the 1990s.”

Call it the chaos theory as applied to politics. In Florida or New York, Donald Trump flaps his wings, and hundreds of miles away, a trio of aging Democrats stir.