Senate candidate Elizabeth Warren delivers DNC speech Wednesday

CHARLOTTE, North Carolina (CNN) -- For a first-time candidate in one of the tightest and most closely watched Senate races, there may not be a better opportunity to raise your profile than a prime-time speaking slot at the Democratic convention as an opening act for former President Bill Clinton

But that's where Elizabeth Warren stood on Wednesday night in Charlotte where she delivered a strident speech that brought a packed convention arena to its feet in thunderous appreciation.

"Americans are fighters. We are tough, resourceful and creative. If we have the chance to fight on a level playing field --- where everyone pays a fair share and everyone has a real shot --- then no one can stop us," Warren said.

A Harvard law professor, Warren is challenging Sen. Scott Brown, R-Massachusetts, for the seat he won in a 2010 special election to replace the late Democrat Ted Kennedy. It has been a tight race for the better part of a year, and Warren aimed key parts of her nationally televised address to Bay State voters.

Warren was best known before her campaign as a watchdog of the government's corporate bailout program, a top financial adviser to President Barack Obama, and the force behind a high-profile agency borne from the 2010 Wall Street reform legislation, the Consumer Financial Protection Bureau.

She focused most of her convention appearance on the middle class, a major theme for Democrats at their convention and on the campaign trail.

"For many years now, our middle class has been chipped, squeezed, and hammered," she said. "People feel like the system is rigged against them. And here's the painful part: They're right. The system is rigged."

While she didn't mention Brown in her speech, Warren went after the more conservative Mitt Romney, Obama's Republican opponent in November who she characterized as an uncompromising ally of Wall Street who would raise taxes on the middle class.

"Mitt Romney wants to give billions in breaks to big corporations --- but he and Paul Ryan would pulverize financial reform, voucher-ize Medicare, and vaporize Obamacare," she said of the former Massachusetts governor and his running mate.

Warren repeated a line she frequently uses on the campaign trail, taking aim at Romney's infamous statement that "corporations are people."

"No, Governor Romney," she said. "Corporations are not people. People have hearts, they have kids, they get jobs, they get sick, they cry, they dance. They live, they love, and they die. And that matters."

Well under way for about a year, Warren's race is one of the most expensive Senate campaigns in the country. Since entering the contest, Warren has raised a massive $28 million, with Brown also taking in more than $19 million.

The question now is whether her speech will give her a boost to put her ahead of Brown.

When Warren entered the contest a year ago, she quickly rose to the ranks of widely known and beloved Democrats, having already been a target of congressional Republicans for taking on Wall Street, a key GOP constituency.

Political observers have described the race as crucial for determining control of the Senate. Democrats hold a four-seat margin in the 100-seat chamber. Additionally, two Independents reliably caucus with Democrats.

The Senate campaign has largely grown into a competition over which candidate is the toughest advocate for everyday people. Republicans, however, try to frame her as a liberal ideologue with little to no centrist appeal.

Warren got big spotlight at the convention, while Brown has not tied himself so closely to his party.

Brown didn't make a high-profile speech at last week's GOP convention and he is less than shy about asserting his independent spirit as a Republican in typically Democratic Massachusetts. He launched a website this week critical of Warren on taxes and other issues.

CNN's Paul Steinhauser contributed to this report.

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