“Unity is the key,” said the GOP strategist. “You go to the path of least resistance, and tell the rest of the conference, ‘We’re not going to give Susan Collins s**t because she’s expressing openness to certain things.'”

McConnell’s plan has to be flexible enough to account for Trump’s divergence of support across the country, allowing candidates to embrace him where he’s popular and ignore him where he’s not…

That calculation explains the difference in approach between Sen. Martha McSally of Arizona and Sen. Cory Gardner of Colorado. While McSally has explicitly courted the Trump base, Gardner has been practically invisible during the run-up to the impeachment trial.

Whatever the difference in strategy, one thing is clear: no vulnerable Republican can afford to criticize Trump.

“The threat of crossing Trump and going against him weighs more heavily on the minds of these senators than reaching to the middle,” said Jessica Taylor, the Senate and governors editor at the nonpartisan Cook Political Report. “Republicans cannot afford to depress Republican enthusiasm by crossing President Trump.”