Two and a half weeks ago, Newark Mayor Cory Booker (D) made two things clear: He’s not challenging Gov. Chris Christie (R) this year, and he’s seriously exploring a run for the Senate in 2014.

What’s become less clear in the short time since Booker addressed his political future is how he fits into the 2014 Senate picture. Sen. Frank Lautenberg (D) has left the prospect of another campaign on the table while a well-funded member of the House also has reportedly expressed interest in the seat.

Both developments represent significant potential hurdles for Booker.

Newark Mayor Cory Booker (D). (Mel Evans/AP)

Consider that in the time since Booker made his announcement, the following things have happened:

* Lautenberg’s spokesman released a terse statement that same day declaring, “This is not the time for political distractions and the Senator will address politics next year.”

* Multiple reports have indicated that Rep. Frank Pallone (D) also is making preparations for possible a Senate bid. Pallone had nearly $3.5 million cash on hand through late November.

The words Booker chose in his announcement video were deferential to Lautenberg. “I look forward to consulting with Sen. Frank Lautenberg. It would be a privilege and honor to continue his legacy of service,” the mayor said.

But his willingness to express such strong interest in Lautenberg’s seat before the senator announced his future plans was, on the whole, a pretty bold move. Yes, Lautenberg is about to turn 89 and might well retire. But he hasn’t said so yet, so Booker’s announcement applied new pressure on the senator to make a decision.

One Garden State political strategist said he doesn’t think most Democrats begrudge Booker for moving toward a Senate run, but that the mayor’s decision not to challenge Christie disheartened some in the party.

“There's some disappointment that he is not taking on Chris Christie, because that would have been a terrific race,” said New Jersey Democratic strategist Paul Swibinski.

For his part, Booker said he is making an effort to open the lines of communication with Lautenberg, whom he says has "a decision to make." “We've reached out to [Lautenberg] a number of times," said Booker in a Monday interview on CNN. "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."

Even if Lautenberg retires, Booker could face a serious threat in a Democratic primary in Pallone. If congressman also gets in the race, Booker would be facing a proven fundraiser with an ability to win swing voters.

“Pallone is formidable because he represents the center of the state including some shore communities. It's a very independent, swing kind of area,” Swibinski said.

Of course, Booker’s own strengths shouldn’t go overlooked. A rising star, he’d have no trouble raising money or finding high-profile Democrats with national profiles to back his bid. A recent survey from Democratic automated pollster Public Policy Polling showed that a majority of New Jersey Democrats favor Booker to be their candidate when matched up against Lautenberg.

A Democrat close to Booker told The Fix that the interest from other potential candidates in the Senate race comes as no surprise.

“I don’t think things are playing out any differently than we thought they would play out here. We are going to be prepared for a Senate run, should the mayor decide to do that," the Democrat said.

As Booker weighed both a Christie challenge and a Senate bid, there were some clear political reasons for him to choose the latter, including Christie’s recently sky-popularity in the Garden State.

But the Senate’s not shaping up to be a sure bet. And if the last couple of weeks are any indication, Booker’s path to the upper chamber could be pricklier than it once seemed.