A fundraiser hosted by Facebook founder Mark Zuckerberg for New Jersey Gov. Chris Christie generated headlines and speculation that the billionaire could ultimately bankroll the Republican's rumored presidential campaign. But one of Christie's peers and rivals got a major boost to his own rumored presidential hopes this week: Newark Mayor Cory Booker.

Veteran New Jersey Sen. Frank Lautenberg announced his retirement from politics, saying that his current term will be his last. In doing so, he paved the way for Booker to run for Senate. Booker had already announced that he would seek the seat before Lautenberg's plans became clear -- a move that, according to sources, irritated the 89-year-old senator.

By retiring, Lautenberg will help both Booker and the national Democratic Party avoid what could have been an ugly and costly primary fight -- costly in money but much more costly to Booker in terms of image. Some believe that Gov. Mitt Romney's 2012 presidential hopes were dashed long before he ever faced off with President Obama, thanks to a brutal and long Republican primary in which he suffered endless attacks. Booker is now likely to avoid that morass and garner the support of most serious political donors and political players.

Now the real test for Booker begins.

Booker has long been far more famous and politically prominent than usually makes sense for a local mayor. There is no mayor in America more famous than he, except perhaps the mayor of New York, Michael Bloomberg, who is a generation older than Booker and a billionaire.

Booker's fame has, in many ways, existed beyond the limitations of his title because everyone accepted that he was not going to stay in that position for long. The question of Booker's political ascension has always been when he would move to a national political role, not if. This perception has aided Booker in many ways, affording him opportunities that few mayors enjoy. (Quick question: How many other mayors can you think of off the top of your head who have appeared on Meet the Press?) For a time, he was predicted to be the first viable black candidate for president, before anyone had heard of a guy named Barack Obama.

But lately this perception has proved to be a political liability. The New York Times published what was largely seen as an extremely unflattering profile of Booker, which gave credence to critics who have long insinuated that he is merely using Newark as a stepping-stone to his real goal: the White House. Booker took the criticism very seriously and, some thought, personally. But what was notable about the fracas is that it was Booker's first real taste of the pitfalls that go with finally becoming a bona fide national political player, not simply a local figure who occasionally gets to play one on TV.

Should Booker win Lautenberg's Senate seat, which isn't unlikely, he will be, in the eyes of many, one step closer to the White House, but that largely depends on how he weathers being under the national spotlight full time. Plenty of onetime future presidents have wilted under the national spotlight, from former New York Mayor Rudy Giuliani to former North Carolina Sen. John Edwards. Granted, both of them had complicated personal lives, but that raises another complication that Booker now faces as he ascends: Little is known about his personal life, something that experts say presents a challenge for aspiring presidents.

But first things first: Booker has to win his first nonlocal campaign. Thanks to Lautenberg, that just got a lot easier. 

Keli Goff is The Root's special correspondent. Follow her on Twitter.

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