Hillary Clinton Campaign Flexes Muscle Ahead of Possible Biden Run

— -- Joe Biden has yet to make a decision about jumping into the 2016 presidential race, but Hillary Clinton already seems to be running against him.

This morning, Clinton's campaign blasted out a press release boasting that 50 African-American mayors from across the country would be endorsing her for president today.

While Clinton's campaign didn't "cc" the Vice President on the email, it might as well have.

The announcement -- which included the endorsements of more than 25 mayors from South Carolina, a state where Biden would likely hope to make gains -- is just the latest move by the Clinton campaign to flex its muscles and tout its strength in the face of Biden's indecision.

Following her strong performance at the first democratic debate, which some pundits observed may have closed the door on a Biden run, Clinton has highlighted aspects of her campaign that might make Biden think twice before jumping in.

Last week, the campaign touted another backing from a large union, her early endorsement from rising Democratic star HUD Secretary Julian Castro and $33 million cash on hand --more than any other presidential candidate.

This week, in addition to the mayoral endorsements, the campaign also announced that 90 Texas Democrats have backed Clinton, and, most notably, that they’re officially bringing out the big guns: Bill Clinton.

The former president will make his first visit to Iowa of the campaign for a rally for his wife on Saturday, alongside Katy Perry.

Although Clinton hasn't attacked Biden directly, her actions are sending a subtle, but clear-eyed message to him: I dare you to run.

Even her campaign chairman John Podesta is sending signals. "If Vice President Biden wants to enter and compete for the presidency, then it is time he make that decision,” he said recently. .

Biden has also started to square off against Clinton. Clinton's camp and reps for Biden did not immediately respond to requests for comment.

The vice president took what could be perceived to be a dig at Clinton on Monday when he said that "I don't consider Republicans enemies, they're friends.” During the debate, Clinton cited "the Republicans" as the enemy she's most proud of.

And on Tuesday, he changed his story regarding the Osama bin Laden raid -- saying that privately he had encouraged the president to support the raid, even though he had expressed skepticism in public. (Hillary Clinton, who often discusses this raid on the campaign trail, has touted that she was in the group of advisers that had supported it.)

Although speculation about Biden's run has reached fever pitch, it's still unclear when he will make his final decision — and two new polls could give him pause.

An ABC News/Washington Post poll released today shows Clinton has 54 percent support among Democrats compared with Sanders’ 23 percent and Biden’s 16 percent. That’s 12 percentage points better for Clinton than her position a month ago, bringing her halfway back to her level of support in the spring and summer, before her September stumble.

And a CNN/ORC poll released yesterday shows 47 percent of Democrats say they want Biden to jump in, while 49% of Democrats say they want him out.