Hillary Clinton sparked fresh speculation she wants Senator Elizabeth Warren of Massachusetts as her running mate appearing alongside her before supporters in Cincinnati, Ohio.

In fiery, energetic form, Ms Warren began by taking pitiless aim at Donald Trump, the presumptive Republican nominee, dismissing him to loud cheers in the hall as a “small insecure money-grubber, who fights for no one but himself”.

“What kind of a man,” is Mr Trump, she asked, kicking off one of the most electric events hosted by Ms Clinton in many weeks. “A nasty man who will never become President of the United States because Hillary Clinton will be the next President of the United States…because she knows what it takes to beat a thin-skinned bully who is driven by greed and hate.”

As the throngs in the room started chanting Ms Clinton’s first name, so Ms Warren, who showed off her flinty populist side, interrupted her own address to join them. “She has brains, she has thick skin and steady hands, but most of all she has a good heart and that’s what America needs,” she declared. “Are you with her?” she went on, eliciting a roar from the hall.

If the political chatterers were seeking signs of how well the two would blend, they didn’t have to look further than their wardrobes. Both women were in almost identical shades of blue. On the other hand, is there risk the feisty energy of Ms Warren could eclipse the more deliberate Ms Clinton? Before the rally, the two women met for talks in Ms Clinton’s hotel room.

But Ms Warren, a former watchdog of consumer financial rights for President Barack Obama, offers above all to reinforce the progressive credentials of a Clinton ticket and help draw in the liberal left who are still disappointed by the fading out of the Bernie Sanders campaign.

“Donald Trump says he will make America Great America,” she told the rally. “It’s stamped right there on his goofy hat. You want to see goofy, look at him in that hat. But when Donald Trump says ‘great’, I ask, great for who exactly? Great for the guys who always want more…watch out, he will crush you into the dirt to get whatever he wants. That’s who he is.”

She also criticised Mr Trump for his reaction to the worldwide recession almost a decade ago and his support of British voters' decision to leave the EU in last week's referendum. “Donald Trump cheered on Britain’s current crisis, which has sucked billions of dollars out of your retirement accounts because, he said, hey, it might bring more rich people to his new golf course.

“He cheered on the 2008 housing crash because he could scoop up more real estate on the cheap. What kind of a man does that? What kind of a man roots for people to lose their jobs, to lose their homes, to lose their life’s savings? I’ll tell you what kind of a man. A small, insecure, money grubber who fights for no one but himself.”

Paying tribute to the Senator, Ms Clinton said she was “so terrific, so formidable because she tells it like it is”. She went on: “I want to thank her for fighting every single day for families like her and families like yours and millions of Americans who deserve to have more folks their side.” Interestingly, Ms Warren stood out among Democrat senators not endorsing Ms Clinton during the primaries.

Ms Warren has competition of course for the number two slot. Among others known to be on Ms Clinton’s shortlist and already reportedly subject to the usual vetting process are Senator Tim Kaine of Virginia and Julian Castro, the Housing Secretary and former Mayor of San Antonio.

“I confess, I can be a little wonky,” Ms Clinton offered. “If you are running for president you should say what you want to do and how you will get it done…best I can tell he has no credible strategy for creating jobs.”