Paul Ryan's tentative agreement to serve as House speaker has set off an era (or at least a day) of unbridled optimism among Republicans.

A new age of Republican unity is here! Paul Ryan will save us!

Not to rain on that parade, but there's some compelling evidence to suggest that many of the problems that dogged Speaker John Boehner could well linger during Speaker Ryan's reign (assuming that the Wisconsin Republican's conditions to be speaker are even met). This chart — via my friend (and Republican lobbyist) Bruce Mehlman — documents how often House Republicans were on Ryan's side on six key votes in 2015.

What the chart shows is that there are between 20 and 45 Republican members who make it their mission to defy the wishes of the party leadership. That has been a very good business model for the Freedom Caucus, which has turned itself into a high-profile power-broker on virtually every contentious legislative fight in Congress. It's less reassuring for the new speaker.

Now, Ryan, if he becomes speaker, will probably have better relations with the Freedom Caucus and others grouped on the far right of the party than Boehner does. But, as the conservative pushback against Ryan over the past 24 hours shows, it's hard to imagine him (or anyone) uniting the fractious groups within the party — especially because he and Boehner have voted in lockstep on key measures this year.

Ryan gives the party its best chance, by far, to move forward with some semblance of order. But, best chance is not the same thing as virtual certainty. It's uniquely possible that the change from Boehner to Ryan — if it comes to pass — will represent a lot less change in how the House operates than many establishment Republicans are hoping.