Is Elizabeth Warren Too Liberal for the Campaign Trail?

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She has been in the Senate for less than two years, but Sen. Elizabeth Warren's tough talk on banks and Wall Street has made her a progressive icon, with her supporters urging her to consider a future presidential bid.

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Warren, a Massachusetts Democrat, has become a popular visitor on the midterm campaign trail, most recently appearing with Kentucky Democratic Senate nominee Alison Lundergan Grimes in the Bluegrass State.

Her fundraising ability is enviable in the high-spending election cycle: She has raised $2.3 million for 28 Senate Democrats, according to her Senate office.

But in tight state races, could a true-blue liberal like Warren be a liability for Democrats?

In West Virginia, where Warren, 65, will campaign with Democratic Senate candidate Natalie Tennant July 14, Republicans are hoping Warren's support for the Obama administration's recently proposed carbon emissions caps will cast Tennant as an enemy of the state's coal industry. (Both Tennant and Grimes support the coal industry and have promised to challenge the White House's position.)

"Just like Elizabeth Warren, Natalie Tennant is bad for coal and bad for West Virginia," said Amy Graham, a spokeswoman for Rep. Shelly Moore Capito, R-W.Va., Tennant's opponent.

Kentucky Republicans have churned out Warren-themed attack ads. In an ad launched Friday by Republican super PAC American Crossroads, Warren is described as "President Obama's biggest fan" and a "war on coal enthusiast."

"Liberals unite," the ad says over a screen showing both Warren and Grimes. "Stop them this November."

While Warren's environmental positions may stir controversy in the two coal states, Democrats say they are banking on Warren's middle-class credibility with voters on economic issues.

"There's coal, there's guns, the social issues are where [Warren's] upside down," veteran Democratic strategist Dave "Mudcat" Saunders said. "But when she starts talking to economic fairness, she's hitting an awful lot of people in the heart."

By focusing on her economic message, Warren can help "change the conversation" of the race for Grimes, according to longtime Kentucky political columnist Al Cross.

"As long as we're talking about coal, Grimes isn't gaining any ground," Cross said.

In Louisville, Warren didn't hide from her differences with Grimes when she said, "Alison and I don't agree on everything."

But on a trip announced after Minority Leader Mitch McConnell, R-Ky., and Senate Republicans blocked her student loan bill that would have allowed refinancing at lower interest rates, Warren said she and Grimes "agree that there is a lot on the line," and that they "want to work together whenever we can."