Audience members cheer at a rally for Republican presidential candidate Donald Trump in Boca Raton, Fla. His presence is leaving party veterans in Congress anxious about their primary prospects. (Paul Sancya/AP)

The next set of canaries will be sent into the coal mine Tuesday.

That’s when another clutch of veteran congressional Republicans will find themselves in primary contests they’re favored to win, but they are still anxious about them because of the anti-Washington turbulence in the GOP embodied by Donald Trump’s presidential campaign.

Among others, there’s Sen. Richard Burr (R-N.C.), chairman of the Intelligence Committee; Rep. John Shimkus (R-Ill.), a nearly 20-year veteran who’s also angling for one of the most coveted gavels in Congress; and, in a highly symbolic race that doesn’t involve incumbents, a tea party bid to claim the seat left vacant by the retirement of former House speaker John A. Boehner (R-Ohio).

These undercard races won’t attract anything close to the attention of Trump’s bid Tuesday to claim the presidential primary battlegrounds of Florida, Ohio and three other large states, but they are the focus of an inordinate amount of attention in the Capitol’s second-floor offices of Senate Majority Leader Mitch McConnell (R-Ky.) and House Speaker Paul D. Ryan (R-Wis.).

McConnell, in particular, is paying close attention to these House and Senate primaries, the margins that the incumbents win by and what they did to win. Unable to influence the outcome of the presidential race — in which another outsider, Sen. Ted Cruz (R-Tex.), a longtime antagonist of McConnell, is so far the only viable challenger to Trump — the GOP leader is putting an intense focus on these early congressional primaries to see whether the presidential candidates are bringing out voters who also want to throw out their members of Congress.

In this 2013 file photo, Rep. John Shimkus, a Republican from Illinois, speaks on Capitol Hill in Washington. Shimkus is one of several veteran congressional Republicans facing primary contests this year. (Susan Walsh/AP)

These early tests will help clarify how rocky things will be for Republicans in the fall, when McConnell’s Senate majority will hang in the balance and, depending on the environment, Ryan’s huge cushion in the House could be reduced to the narrowest of margins. If the establishment canaries can survive, Republican leaders may be a little bit reassured that they can run successful congressional races later this year, independent of whoever tops the GOP ticket in November.

So far, the first clutch of incumbents battled through their March 1 primaries without any casualties.

The takeaway for congressional Republicans is that the incumbents who won the biggest totals ran aggressive campaigns that were well financed and defined their opponents early, using the most modern techniques to reach voters who were also casting ballots for an outsider at the top of the ticket.

It’s a lesson that the Republicans running for president did not apply to their races, something they are paying dearly for now as Trump dominates the field.

“The Trump campaign is real, and some of them ignored that. We could tell that from our early polling,” Sen. Richard C. Shelby (R-Ala.) said last week after his convincing victory.

Shelby is the walking, breathing embodiment of a politician who should be scorned by Trump and Cruz voters: an 81-year-old incumbent, with nearly 38 years in Congress, whose tenure has been marked by close ties to the banking industry and doling out earmarks to favored interests.

He faced several challengers, including a 33-year-old conservative who hoped to keep Shelby below 50 percent of the vote and force him into a runoff that might have prompted deep-pocketed conservative groups from Washington to enter the race.

Longtime Republican Sen. Richard Shelby speaks at his election party after he won Alabama's primary election in early March. Shelby faced several challengers, but won more than 65 percent of the vote. (Brynn Anderson/AP)

Instead, the octogenarian cruised to victory with more than 65 percent of the vote, more than Trump and Cruz combined for in the presidential primary. “We had a lot of people who voted for Trump, voted for me. A lot of people who voted for Rubio, voted for me,” Shelby said, referencing the establishment favorite, Sen. Marco Rubio (R-Fla.).

McConnell has told associates that he was closely watching other races that night, too. The Senate leader was citing the margins run up by GOP Alabama Reps. Bradley Byrne and Martha Roby — first- and third-term lawmakers, respectively — who both took more than 60 percent of the vote.

In Texas, half of the state’s 28 House Republicans faced some level of primary opponent, including robust challenges to three who wield influential gavels: Reps. Kevin Brady, chairman of the Ways and Means Committee; Pete Sessions, chairman of the Rules Committee; and Lamar Smith, chairman of the Science Committee.

Every Texas incumbent won, although Brady had to spend dearly to clear 50 percent and avoid a runoff later in the spring. Sessions and Smith both cleared more than 60 percent.

It’s far from certain that other incumbents will survive.

In 2014, after several embarrassing losses by incumbents in previous elections, Senate Republican leaders ordered their veterans to practice what they called the “Overwhelming Force Doctrine,” running all-out campaigns no matter how minor the competition.

They won every primary, but sitting House Majority Leader Eric Cantor (R-Va.) got caught sleeping and lost in a stunning upset to his tea party challenger, Rep. Dave Brat, in the primary.

In his race, Shelby took nothing for granted. Despite not having a serious race since his first Senate campaign 30 years ago, Shelby had amassed a campaign war chest of more than $20 million, just in case.

Last summer, he sat in McConnell’s office seeking political advice, having watched the leader run a brutal and effective campaign for reelection in 2014 that included overcoming a primary challenge.

Shelby took the unusual step of hiring two polling firms, and the early results made it clear that Trump wasn’t going away. “We knew that, from the beginning,” he said, “he was doing a lot better than people thought.”

By mid-January, Shelby had adopted a lot of political-consultant lingo, using terms such as “soft electorate” to describe those Trump voters who had never really voted in a primary before.

The senator brought on board a digital team led by McConnell acolytes, who waged a tough, below-the-radar campaign against Shelby’s main challenger, John McConnell. For weeks, anyone in Alabama searching the Internet for “John McConnell” saw a website called “Con Man John,” questioning the political neophyte’s business dealings and his position on immigration.

By the time Shelby launched his television ads, created by GOP ad guru Fred Davis, McConnell’s unfavorable rating had spiked by 10 percent.

Then came one last Trump-inspired fear. Sen. Jeff Sessions (R-Ala.), a revered conservative, endorsed the businessman two days before the primary.

But Shelby’s team had already purchased a digital form of Trump insurance: Every person in Alabama who searched for “Jeff Sessions” on Google first saw an ad touting the fact that Sessions had endorsed Shelby. For weeks, only a few dozen people a day saw that ad.

On the day that Sessions backed Trump, more than 11,000 Alabama voters searched for Sessions and discovered that he had also backed Shelby.

It was a completely different fight than he ever expected. But even two years ago, Shelby told The Washington Post he was willing to win, whatever the cost.

“You need to work hard, you need to be heavily armed and you need to take nothing for granted,” he said back then. “If you do that, things work out.”