Cory Booker wasn't talking at all Wednesday about the triumphant power of love.

Instead, Booker, the Spartacus of the Senate, the stand-alone crusader who defied decorum and rules during Supreme Court nominee Brett Kavanaugh's confirmation hearing last year, joined the herd rush of 2020 Democratic presidential hopefuls calling for impeachment proceedings against President Donald Trump shortly after special counsel Bob Mueller's news conference in Washington.

"Robert Mueller's statement makes it clear,'' Booker tweeted shortly after Mueller made his remarks. "Congress has a legal and moral obligation to begin impeachment hearings immediately."

That's a pretty sharp break from Booker's cautious, more deliberative posture of the past few months.

In April, Booker stayed clear of the pitchfork-wielders in the party base. When Massachusetts Sen. Elizabeth Warren, a rival candidate for the nomination, garnered headlines in April calling for Trump's impeachment, Booker played safely to the center, saying "there's a lot more investigation that should go on before Congress" takes that step.

Booker aligned himself with House Speaker Nancy Pelosi, D-Calif, who has tried to tamp down impeachment talk, fearing that an attempt to oust Trump would only backfire and allow him to paint himself as the victim of a Democratic Party witch hunt.

While the Democratic-controlled House might approve articles of impeachment, the Republican-controlled Senate stands ready not to ever convict him. Like Bill Clinton before him, Trump will head to the campaign trail as the battle-hardened survivor, worthy of sympathy and support.

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Booker continued to steer clear of impeachment as late as last week, even as Democratic frustrations with Trump's stonewalling of multiple House investigations were reaching a boil. Trump looked like he was outfoxing the Democrats, leading some to argue that impeachment may be the only way to hold him accountable.

“The House should be allowed to do their work,” Booker told NJ Advance Media last week. “I think right now the president is not cooperating as he should and I believe he’s constitutionally required. I believe we’re going to have a real crisis emerge if he continues to undermine the ability to continue this investigation, which is absolutely critical.”

Booker's pivot to the pro-impeachment pack was notable, especially since the strait-laced Mueller didn't offer anything new in his nine minutes of remarks, other than putting a voice to the one conclusion in his 448-page report that undercut Trump's phony claim of "total exoneration."

“If we had had confidence that the president clearly did not commit a crime, we would have said so,” Mueller told reporters.

So why Booker's sudden change?

For one thing, Booker's "love thy enemy" campaign theme hasn't really caught fire with the party base. He has struggled to burst out of the second tier of candidates with low-single-digit support in the polls and has lagged behind others in his small-donor fundraising.

"It's not that he's sliding. He never took off,'' said Patrick Murray, director of the Monmouth University Poll, which is tracking the 2020 race.

Booker defenders say he's in for the long run, and that he'll emerge as the centrist alternative after Joe Biden fades (or fumbles) and front-runner Bernie Sanders loses steam once the party realizes that it can't afford to have a socialist as the party standard-bearer.

Yet, with the exception of young voters, Biden has shown surprising resiliency among a wide cross-section of Democratic primary voters, including African-Americans, a constituency that Booker has aggressively courted.

And Booker, who five years ago was the rising star of the Democratic Party cheered on by Silicon Valley entrepreneurs and liberal hedge fund operators, is now competing in a field packed with other rising stars, like Mayor Pete Buttigieg of Indiana, U.S. Sen. Kamala Harris of California and Beto O'Rourke, the congressman from Texas.

Jumping on the impeachment bandwagon gives Booker a vehicle to garner some free attention.

"In an otherwise slow news cycle, it will drive what the coverage is. Why not ride on top of (impeachment) when you know you are not going to have to act on it?" Murray said.

Booker was hardly alone. O'Rourke, Warren, Harris, Buttigieg and Julian Castro, a Texas congressman, all called for impeachment hearings to begin. Sanders gave qualified support for the idea, saying he "supports" the start of hearings if the House Judiciary Committee decides to hold them. Only Biden hewed to the Pelosi line, arguing that "no one would relish what would certainly be a divisive impeachment process."

However, Biden's campaign added that impeachment "may be unavoidable if this administration continues on its path."

Murray said he believes Booker remains a viable candidate who has been eclipsed by an unusually early stampede of candidates. The field is likely to winnow, and Booker has worked vigorously to build campaign operations in Iowa, New Hampshire and South Carolina.

And in a swing through Iowa last week, Booker started drawing sharper distinctions with other candidates, something he has refrained from doing. He took veiled shots at Biden's support for the 1994 crime bill and Sanders' hesitancy in supporting Democratic nominee Hillary Clinton in 2016.

But on Wednesday, Booker also swiftly dropped the distinction of being a cautious skeptic on impeachment. On that score, Booker sounds like everybody else.