dig in

“But it’s also going to be very difficult for him to dig in his heels and wait it out.”

It was very exciting to dig in and uncover the mechanism of this unique plant.'

And at the moment, she is digging in on that.

Philip Bump at the Washington Post reported that the House is digging in its heels on their part of the recess appointment gambit as well:

As the conference approached its scheduled end this week, the U.N.’s climate chief chided negotiators for digging in their heels and wasting time with bluffing and brinkmanship.