CHARLOTTE, N.C. — Democrats love Elizabeth Warren. The Massachusetts Senate hopeful took the stage here tonight to a welcome befitting the superstar she is among the Democratic base.

“War-ren, War-ren, War-ren,” the crowd roared.

And the applause and cheers for her only grew louder as she addressed the huge crowd at the Time Warner Cable Arena. Warren, a Harvard professor and consumer advocate, delivered a strong speech. She introduced herself to the prime-time television audience, lauded President Barack Obama and knocked Mitt Romney’s economic plans.

Warren spent most of her speech empathizing with the struggle of middle-class Americans, telling them that the system was “rigged” against the little guy. But Warren assured the audience in the arena and in living rooms across the United States that, unlike Republicans, she and Obama had their backs.

But even as Warren’s speech was greeted with raucous applause here and is sure to be a boon to her already extraordinary fundraising, Democrats back in Massachusetts are increasingly worried about her campaign against Republican Sen. Scott Brown. While Warren has the enthusiastic, unwavering support of the her party’s base, her strength among the rest of the Bay State’s electorate is less certain.

The sense among influential Democrats in the state is that Warren only has two or three weeks to refine her message — in person and on TV — so that it better connects with the independent-leaning Democrats and unaffiliated voters she’ll need to win over to unseat Brown. After that, the path to the Senate will grow increasingly difficult, barring a game-changing external event or revelation.

Though her speech here tonight echoed themes she’s talked about since she launched her campaign, it was delivered with an intense passion — and got a fiery response — that may help propel Warren into her final campaign lap.

“Our middle class has been chipped, squeezed and hammered,” she said, echoing a common stump speech line. “People feel like the system is rigged against them. And here’s the painful part: They’re right. The system is rigged.”

She cited subsidies to oil companies, rich people paying lower taxes than their secretaries and Wall Street CEOs “strut[ting] around Congress, no shame, demanding favors and acting like we should thank them.”

But, Warren explained, the president was working to make sure everyone had a fair shake on “level playing field.”

“He believes in a country where everyone is held accountable. Where no one can steal your purse on Main Street or your pension on Wall Street,” she said.

Warren took direct aim at Romney.

“Republicans say they don’t believe in government. Sure they do!” Warren said. “They believe in government to help themselves and their powerful friends. After all, Mitt Romney’s the guy who said, ‘Corporations are people.’”

“No, Gov. Romney, corporations are not people,” Warren said to cheers. “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.”

The crowd went wild.

Warren is locked in a fierce battle with Brown. Recent polls have found the race to be in a dead heat. But Warren never mentioned her GOP opponent, instead focusing on the national issues that she appears to hope will define her race.

Her prime-time speaking slot here stood in stark contrast to Brown’s role at the Republican National Convention in Tampa, Fla.,  last week. The Senator made only a short appearance in that city and had no speaking gig.

Brown has worked hard to paint himself as an independent voice for Massachusetts, aligned with his party only when it is in the best interest of his constituents. So his limited role in Tampa made sense: Even the appearance of closeness to Romney, a fellow Bay Stater, and the party apparatus now would be politically damaging for him.

Massachusetts will almost certainly vote for Obama by a large margin this November. And it was clear tonight supporters of the president were also supporters of Warren.

Back in Boston, it’s not only Democrats who are a little nervous about the race.

There’s caution from Bay State Republicans, too. They are closely watching Warren’s ability to make the race a referendum on national issues rather than personality, a turn of events that would be bad news for Brown, who remains well-liked in the Bay State even as Republicans aren’t.

“She’s speaking at the convention, in part because she is seeking to nationalize the race,” veteran Massachusetts GOP consultant Rob Gray said. “That’s probably the linchpin for her, if she can pull it off: to convince voters, even if it’s not entirely accurate, that Brown is tied in with Washington Republicans who want to stop the Obama agenda.”

But tonight, Warren made her speech about more than just Democrats and Republicans. She did her best to make it about contrasting visions for the future of the middle class and the country.

Toward the end of her speech, Warren quoted the Bible.

“I grew up in the Methodist church and taught Sunday school,” she said. “And one of my favorite passages of scripture is: ‘Inasmuch as ye have done it unto one of the least of these my brethren, ye have done it unto me.’ Matthew 25:40. The passage teaches about God in each of us, that we are bound to each other and we are called to act,” she said.

“Not to sit, not to wait, but to act,” Warren told the arena, “all of us together.”