That doesn't mean Republicans are sanguine about Trump's low approval ratings nationally, an energized anti-Trump progressive base and the potential for more damning revelations from the Russia-related investigations -- a potentially toxic brew, especially in the more moderate districts that could determine control of the House of Representatives.
"Republicans should keep in mind that we essentially ran the successful 2010 election cycle as a referendum on President Obama," said Ryan Williams, a former spokesman for 2012 GOP presidential nominee Mitt Romney. "We were able to defeat congressional Democrats by running against his record. We didn't know how good a year that was going to be until Election Night. The midterm election of a president's first term is usually challenging to begin with for the party in power."
As he watched Mueller-related developments play out on television during an interview last week, Williams said, "Other events could potentially make it even more challenging."
Like most operatives interviewed for this piece, veteran GOP pollster Whit Ayres stressed that it is far too early to make predictions about what messages will be effective in shaping the midterm elections. But he said the president's standing traditionally does matter.
"What we know is, historically, the president's party performance in midterms is affected by the president's approval rating, there's a well-established historical correlation at this point," he said. "The approval rating affects the overall political atmosphere of the country. It's the backdrop on front of which congressional campaigns play out."
Meanwhile, Democrats have been at odds for much of Trump's presidency over whether to focus more on pocketbook issues or to try to make the midterms a referendum on the president -- though the latter tactic alone did not work in 2016 against Trump, they acknowledge.
Jesse Ferguson, a top Democratic strategist, expects the strongest Democratic messaging to be aimed at Republican-controlled Washington as a whole.
"That means Trump. It also means (House Speaker Paul) Ryan and McConnell," he said. "It means they own the 'swamp,' and they've poured more water into it. If you're a voter who thinks Washington isn't delivering for you, or that Washington is captured by the culture of corruption and cover-up, then you vote against the Washington creatures that are running it. Certainly the focus of that is the president, but there's nothing in Washington that isn't Republicans' responsibility and Republicans' fault."
(And indeed, when asked about the party's 2018 approach, Ben Ray Lujan, chairman of the House Democrats' campaign arm, wrote an editorial that was not focused on Trump, instead arguing that voters want change in GOP-run Washington.)
On the question of responsibility, many Republicans agree. But they see that argument translating, more immediately, into a referendum on what the GOP has to show for its majorities, rather than on Trump-related controversies, as Congress scrambles to land a tax reform package, desperate to claim a major legislative victory after failing to repeal and replace Obamacare.
"I largely don't think it will be a referendum on Trump, I still think it will be a referendum, or validation, on the Republican Congress," California-based Republican strategist Rob Stutzman said. "I'm not a big fan of the president's, but he's not on the ballot."
In congressional primaries, many candidates are already scrambling to paint themselves as the contender best-positioned to promote Trump's agenda, often criticizing Republicans who have clashed with Trump at times -- from McConnell to Sen. John McCain.
"It's going to be two stages," said one top party strategist. "You have the Republican primary stage that is absolutely a referendum on what's getting done in Washington and what Republicans are doing to help the president's agenda."
"It's a little bit different in the general, in the same way a lot of these first midterms during the first term of a president's time in office is a referendum on them," that GOP source said. "But more than that, it's going to be a referendum on what has been accomplished. If Republicans cut taxes, they can hang onto the House. If they can't they're going to lose in a really big way."
(c)2017 McClatchy Washington Bureau
Visit the McClatchy Washington Bureau at www.mcclatchydc.com
Distributed by Tribune Content Agency, LLC.