When it comes to reauthorizing bulk data collection, nearly a dozen conservative senators are stuck in a tug of war between Republican Majority Leader Mitch McConnell and their libertarian-minded colleagues, reform advocates, and constituents back home.

With just a matter of hours to go before the Senate is expected vote on the USA Freedom Act, which would end the NSA's bulk collection of call data, Republican Sens. Kelly Ayotte, Joni Ernst, Tim Scott, Mark Kirk, Pat Toomey, Bill Cassidy, and Ron Johnson are still publicly not saying where they stand on the legislation, putting the future of the NSA program in limbo. Sen. David Perdue says he has made up his mind, but he too is staying mum on how he would vote.

An aide to Judiciary Chairman Chuck Grassley emailed late Thursday to say the Iowan would vote against the Freedom Act.

"There is a chess match game being played," Cassidy said. "I want to see how those pieces are being moved."

Supporters of the USA Freedom Act said Friday that they were inching closer to securing the 60 votes they needed to overcome a procedural hurdle, but they are up against the clout of Republican leaders who are still confident the bill won't have enough votes.

That has unleashed an all-out lobbying effort on Capitol Hill as the White House, tech reform groups, Republicans, and Democrats alike make their final appeals to wavering colleagues. The White House met with a bipartisan group of senators in the Situation Room Thursday, including Democratic Sen. Joe Manchin and Republicans Jeff Flake and Ayotte.

Reform Government Surveillance, a group of tech business leaders including Google and Facebook, released an open letter urging members to "pass meaningful and balanced surveillance reform" this week, and GOP Sen. Steve Daines of Montana said he's personally taken on the task of convincing his fellow freshman Republicans to get behind the USA Freedom Act or risk letting a national security program cease to exist in any capacity.

"I've seen some movement," Daines said, noting freshman Sen. Cory Gardner's announcement that he would get behind the bill.

Across the Capitol, House Judiciary Committee Chairman Bob Goodlatte has been working overtime to reach out to senators.

"As a former House member, I think there is some wisdom there," Scott said Thursday night of his own discussions with Goodlatte.

But undecided Republicans were given another option Friday afternoon when Senate Intelligence Chairman Richard Burr unveiled a framework for "compromise" legislation that would stretch the transition away from the NSA's current bulk regime to two years and make two other Patriot Act spy authorities permanent. The Freedom Act would transition away from the bulk dragnet after 180 days.

But Freedom Act supporters immediately denounced Burr's plan as implausible. A pro-reform Democratic aide described the proposal as an unrealistic offering only meant to cajole undecided Republicans to his side by giving them a "plausible excuse" to vote down the Freedom Act.

"I don't know who he's trying to appeal to with this," the aide said. "His counter offer to ending bulk collection is to extend bulk collection for two years."

Still, Burr's last-minute push appeared to be paying off, at least with some Republicans. Sen. Rob Portman of Ohio said Thursday he would probably vote against the Freedom Act, citing a recent conversation with Burr about his offering.

"Sounds like he has a very interesting alternative that I think probably holds more promise," Portman said.

As the clock runs out, libertarian-leaning Republicans working on behalf of the USA Freedom Act are pointing to the bill's strong support in the House of Representatives and reminding colleagues that if the legislation does not pass the Senate, it is possible that intelligence agencies will be left without access to phone metadata and that the Patriot Act's broader surveillance powers will also go dark. That argument only grows more convincing as House members threaten to stand in the way of any short-term extension.

Senior Obama administration officials directly warned during a Thursday press call against letting several Patriot Act provisions lapse, saying their expiration would put several "critical" national security tools in jeopardy. And Goodlatte, House Judiciary ranking member John Conyers, Republican Rep. Jim Sensenbrenner, and Democratic Rep. Jerrold Nadler released a public warning against any "11th hour" proposals Friday.

But even with all of the outreach, undecided senators say they still are not sure if the USA Freedom Act is enough to protect the United States' national security needs.

"I am still torn. I think we have work to do," Ernst said, noting she was leaning toward supporting a short-term extension instead.

North Dakota's John Hoeven was leaning toward support for the USA Freedom Act and had been conversing with the bill's sponsor, Sen. Mike Lee, R-Utah.

On Friday, Hoeven said he was "likely" to vote yes.

For conservatives, there is a lot at stake. McConnell has been publicly railing against the USA Freedom Act at every turn, even taking the floor Friday morning to remind his rank-and-file where he stood. Voting against McConnell could be a risky move for lawmakers worried about bucking leadership to side with the White House and a rabble-rousing House.

Sen. Johnny Isakson, R-Ga., said he hoped his younger colleagues would come around to see McConnell's side of things before it was too late.

"I was here on 9/11. I saw what happens when you don't have the information you need. I don't ever want to see that happen to America again."

This post has been updated to clarify the circumstances of Thursday night's press call.

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