Newark Mayor Cory Booker said Monday morning that Sen. Frank R. Lautenberg has “got a decision to make” on whether to retire.

The comment, made on CNN’s “Starting Point,” is acknowledgment that the Senate field is far more complicated than he projected during his Senate exploratory announcement. Booker’s candidacy as it stands is a primary challenge of a longtime Democratic incumbent. Lautenberg has yet to announce his retirement, and few in New Jersey have any idea on what he will do.

“I want to give him the space to make his own decision,” Booker said. “I’ve announced my intention to run, but the reality is we’ve got a good Senator. He’s been loyal. He’s been there for a long time. And I think he’s got a decision to make.”

Buzzfeed reported last week

Senate Democrats have been successful at avoiding messy primaries, unlike their Republican counterparts. But Booker’s comments this morning indicate they might not be able to avoid a divisive intraparty fight unless Lautenberg voluntarily decides to step away. Many Democrats had hoped Booker would challenge popular Republican Gov. Chris Christie this year.

“So, I’m focusing on my job for now. And I hope to talk to him,” Booker added. “We’ve reached out to him a number of times. In fact, I had a plane trip going down to meet with him, but unfortunately with a lot of the challenges going down in Washington, he had to cancel the meeting.”