Nick Clegg paved the way for the survival of elements of the snoopers' charter today, after he said the government was "pursuing some parts" of the bill.
The deputy prime minister's comments mark a significant tonal shift from his previous announcement that he would rule out the bill and suggests Theresa May could succeed in enshrining certain parts of it in law.
Clegg said he would not support elements of the bill which would store information about the websites internet users visit but that he supported efforts to link IP addresses to specific mobile devices.
"The issue of storing website addresses everyone visits is an issue of principle. It's just excessive," he told listeners to his weekly LBC programme.
"You need to strike the right balance. I think we're doing that by saying we'll solve this issue.
"The British public want us politicians to strike a very difficult balance of freedom, democracy and traditions of liberty and giving security services and police the tools they need."
Pressure has been building for the snoopers' charter to be revisited since the terror attack in Woolwich last week, with civil servants working on stripping down the original proposals so they can be passed without the need for a Commons vote.
The Liberal Democrats have long-supported the proposal on IP addresses, which featured in the Queen's Speech.
But today's change of tone from the deputy prime minister suggests he is prepared to be more pragmatic about the package of policies than he was before the Woolwich murder.
Liberal Democrat sources told Politics.co.uk the party would still hold fast against the more draconian measures in the bill.
If the Home Office was hoping that Clegg had had a major conversion to its increasingly authoritarian approach to extremism, he will have disappointed them with his views on radical preachers, however.
The Liberal Democrat leader shot down plans by Theresa May to clamp down on extremist Muslims like Arjem Choudary appearing on television by allowing Ofcom to pre-emptively ban them from our screens.
"It's not for politicians to tell broadcasters: 'That person shall not be on'," he said.
"I told [people who complained about Choudary's appearances] 'you should get in touch with the producers of these programmes and say Choudary doesn't represent the vast majority of law abiding Muslims in the world.
"I'm an old fashioned liberal. I think abhorrent ideologies are best defeated when they are argued against, when they are demolished."
Michael Adebowale has been charged with the murder of soldier Lee Rigby in south-east London last week.