Republicans and Trump supporters — up to and including his top aides — seem to be almost constantly faced with a choice: Support your president or take a stand. And whenever one takes a step away from the commander in chief (see: John McCain on Friday and Gary Cohn and Rex Tillerson last week), it's big news.

It also comes with a cost. And the severity of that cost is becoming increasingly clear.

I wrote last week about how limited polling had shown Sens. Jeff Flake (R-Ariz.) and Dean Heller (R-Nev.) losing huge support among the GOP base after running afoul of Trump:

A poll from Democratic-leaning automated pollster Public Policy Polling this month showed a grim state of affairs for Heller, who initially opposed the GOP health-care bill and drew Trump’s ire before eventually supporting a later version. The PPP poll showed him with a brutal 22 percent approval rating in Nevada, compared to 55 percent who disapproved.
Ditto the other vulnerable Republican senator up for reelection in 2018, Flake, who has been a more vocal Trump critic than Heller. Around the same time, PPP had him at just 18 percent approval in Arizona versus 62 percent disapproval. Again, brutal. The reason? Trump voters are almost completely deserting him, with just 22 percent approving of him and 63 percent disapproving.

I said at the time that we needed to see more data before we could say that the GOP base is turning on Trump's allies. Well, we've got more data. And while it doesn't show such a huge revolt, it does show tangling with Trump can cause real problems for Republicans.

After President Trump's rhetoric on the Charlottesville violence inflamed more criticism, a handful of GOP lawmakers are speaking out while many stay silent. (Jenny Starrs/The Washington Post)

A new Fox News poll this week showed Senate Majority Leader Mitch McConnell's numbers taking a turn for the worse after repeated criticisms from Trump. McConnell (R-Ky.) has never been beloved, of course, but his favorable rating among Republicans has now shifted from 42 percent positive and 23 percent negative in June to 29 percent positive and 41 percent negative today. That's a net shift of 31 points (from plus 19 to negative 12) in two months.

Also tellingly, the number of Republicans who have a “strongly unfavorable” view of McConnell has doubled to 19 percent, while those who have a strongly favorable one has declined to just 4 percent.

The story is similar for perhaps the most vocal GOP Trump critic, McCain, who has just written a Washington Post op-ed calling the president “poorly informed” and encouraging fellow senators not to act like the president's “subordinates.”

The Fox poll finds that the senator from Arizona is also underwater among Republicans nationally, with a slim majority (51 percent) having an unfavorable opinion of him and just 44 percent having a favorable one. McCain is actually much more popular among Democrats, where his favorable/unfavorable split is 64/26. Remarkably, the percentage of Democrats who dislike McCain (26 percent) is less than the percentage of Republicans who strongly dislike McCain: 28 percent.

Of course, that's the trade-off you make. Criticizing and opposing Trump may make you a big name nationally and even win over Democrats and independents, but Flake and Heller have to be extraordinarily concerned about how it's playing with their base right now given they both face primary challengers in 2018. And most Republicans in Congress really only have to worry about such primaries, because they don't live in competitive states or districts.

Republicans — including McCain — have been reluctant to go whole-hog in defying Trump. These numbers show exactly why they will continue to be gun-shy.