The reason they may not ultimately do that has to do with the reauthorization of the Patriot Act, which is up for renewal. McConnell is on record for favoring a reauthorization of the bill in its original form, without the changes that the Freedom Act would force.
However, it appears that a bipartisan majority of senators favors the changes created by the USA Freedom Act, so there's a strong likelihood that McConnell won't get the support he needs to reauthorize the Patriot Act in its original form.
His only chance to keep the Patriot Act alive would be to accept the changes created by the Freedom Act. At this point, there is no other legislation in the Senate to reauthorize the Patriot Act in its original form.
"This is a carefully crafted compromise," said Bijan Madhani, public policy and regulatory counsel for the Computer and Communications Industry Association (CCIA). "The chances are good in the Senate," he said.
While the Freedom Act has gathered strong public support from all sides (except for senators from Kentucky), that does not mean everyone is thrilled with it. Madhani said CCIA would like to see more robust controls over the FISA Court and more protection for Americans when their communications are caught up in intelligence aimed at foreign citizens.
There are also many who would rather see the Patriot Act eliminated, including Senator Rand Paul (R-Ky.), who is running for president. A number of tech industry associations, including the CCIA, the Software and Information Industry Association (SIIA) and BSA/The Software Alliance, have voiced approval at the committee passage of the USA Freedom Act. Perhaps more importantly, there are more Senate sponsors this time, than there were when a similar bill failed to pass the Senate by two votes.
While it's not impossible to pass legislation over the strong objections of the Senate majority leader, it is difficult. The chairman holds the reins of power in the Senate, and he can dispatch a bill to oblivion if he so desires. But enough senators can overcome that despite the procedural roadblocks that the majority leader can put in the way. But it wouldn't be easy.
At this juncture, the best chance the Freedom Act has is for the Senate majority to support the bill to make it clear that they are determined they want the Freedom Act and that they're willing to defeat the unrevised Patriot Act.
Mitch McConnell may be stubborn, but he's not dumb. He will likely realize that getting most of what he wants in a bill is better than getting nothing. And the Freedom Act of 2015 is a lot better than nothing at all.