Let’s give it up for Marco Rubio! After months of getting his butt whipped in the rabid-obstructionism department by Ted Cruz, the junior senator from Florida emerged the hands-down winner in the race to trash the Murray-Ryan budget deal. The entire political chattering class expressed awe this week at just how quickly Rubio’s team pushed out his “this deal sucks” statement. It was as though some poor staffer had been assigned to sit around 24-7 with his finger hovering over the “send” button, just waiting for the deal to drop.

Not that Rubio’s victory was one merely of speed. He lapped the field on intensity as well, pursuing an impressively aggressive schedule of media denunciations: Huckabee, Hannity, Megyn Kelly—even a full-on column on Breitbart.com, warning of how the deal was further threatening the American Dream. No way anyone can mistake where Rubio stands on this issue. He is 100 percent opposed to derailing the American Dream by allowing sequestration to be tinkered with.

Now, some might find Rubio’s current attachment to sequestration a bit rich, seeing that he opposed it a couple of years back. And not just kinda, sorta opposed it. Two years ago this week, Rubio was among the handful of Republican senators decrying the damage that such “arbitrary fiscal arithmetic” would have on our national defense and vowing to find a smarter alternative. Small wonder that Commentary’s Pete Wehner felt moved to marvel this week, in a column titled “Marco Rubio and the Perils of Opportunism”: “Now he’s criticizing a budget deal that would increase spending on defense while also slightly cutting the deficit, arguing that we shouldn’t give up the sequestration deal that he initially opposed. And he’s the one complaining about a lack of ‘long-term thinking.’”

This is not to suggest that Wehner—or anyone else for that matter—is remotely puzzled by Rubio’s behavior. As Wehner goes on to observe: “Senator Rubio strikes me as a person not only highly attuned to criticisms of him from the base, but overly reactive to them, adjusting and responding moment by moment. One senses that believing he badly hurt himself with the base because of his stand on immigration, he’s now scrambling to ingratiate himself with it. It isn’t a particularly impressive thing to watch.”

On this point, I have to disagree with Wehner. Even by the debased and debasing standards of modern politics, Rubio’s frenzied, shameless pandering to the GOP base is more than impressive; it’s genuinely breathtaking. Forget his current Cassandra act on the budget deal. Recall how brutally he threw his own immigration bill under the bus when it became clear that it was costing him support among conservatives. The Gang of 8 compromise passed the Senate in late June; by late October, Rubio was running around lecturing every reporter he saw about the need to ditch it in favor of the more “realistic” go-slow, piecemeal approach favored by House Republicans. As Rubio’s spokesman, Alex Conant, put it to TPM.com: “We should not allow an inability to do everything to keep us from doing something.” (The senator’s office declined to comment for this story.)

Ah, yes. Marco Rubio. Political pragmatist. Except when it comes to this week’s exceedingly modest budget compromise—then suddenly the man is as pure as the driven snow: a slash-spending, overhaul-government, brook-no-compromises, go-big-or-go-home guy.

No question these are fraught times for Republican lawmakers—especially those who fancy themselves contenders for 2016. But Rubio needs to tread carefully when executing such dramatic and blatant panders. It’s hard to convince the electorate that you’re a man of principle when you’re so visibly soaked in the cold sweat of desperation.