In this June 29, 2014, photo, U.S. Sen. Elizabeth Warren, left, and Kentucky Democratic senatorial candidate Alison Lundergan Grimes wave to supporters at a rally in Louisville, Ky. (Timothy D. Easley/AP Photo)

Republican or Democrat, everyone wants Elizabeth Warren to hit the campaign trail - but for different reasons.

Today is a big day on the 2014 trail in West Virginia, with both Rep. Paul Ryan, R-Wis., stumping for GOP Senate candidate Shelley Moore Capito and Sen. Elizabeth Warren, D-Mass., campaigning with Democratic Senate candidate Natalie Tennant. It's Warren, though, who has both sides excited about her trip - and this isn't the first time Warren has sparked bipartisan hubbub with a foray into a competitive race.

She's popping up in red states, where Republicans paint Warren (and whoever she may be stumping with) as anti-coal liberals, but that hasn't stopped her from being hotly requested on the Democratic campaign trail for 2014 candidates. Most recently she stumped with Kentucky Democratic Senate nominee Alison Lundergan Grimes last month, raising over $200,000 for her campaign at a fundraiser.

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GOP groups have jumped on Warren and Tennant since the event was first announced and continued to hammer her today.

"Warren's presence in West Virginia will only further alienate Natalie Tennant from voters who see her as a defender of President Obama and his anti-coal agenda," Capito's campaign said. And Ryan told reporters at the Capito event today that Warren is "to the left of the left of the Democratic Party," adding she is "part of the war on coal."

In a Web video out today, the Karl Rove-backed Republican super PAC American Crossroads calls Warren the "queen of class warfare" and over images of both Warren and Tennant are the words: "Liberals unite. Stop them this November." The group ran an almost identical video last month featuring Warren and Grimes.

On the stump, Warren pointed out that she and Grimes "don't agree on everything," something she has also said about Tennant. That's because both Tennant and Grimes have consistently criticized the Obama administration's plans to limit carbon emissions from the coal industry, something Warren supports, which Republicans are eagerly pointing out.

The National Republican Senatorial Committee joined in, calling Warren "liberal and extreme" and saying that Tennant, West Virginia's secretary of state, is "working to prevent voters from realizing Warren's notoriously anti-coal record."

So, shouldn't Warren be persona non grata on the Democratic campaign trail? The answer is just the opposite.

In the last four months, in addition to Grimes in Kentucky, Warren stumped for Sen. Al Franken in Minnesota and attended fundraisers for Sens. Sherrod Brown in Ohio, Jeff Merkley in Oregon, and Patty Murray Washington. She will also travel to Michigan this week for a fundraiser with Michigan Democratic Senate candidate Gary Peters , and has sent out fundraising emails for Democratic Senate candidates in Iowa, South Dakota, New Hampshire, Arkansas and Georgia.

Why is she so in demand, despite being a GOP target? Democratic strategist Mary Ann Marsh, based in Warren's Massachusetts, says it's because "nobody has been a bigger voice on making sure that we not only get the economy back on track and people on their feet, but also be given a fair shot at getting a good job and getting paid for a good job to support their families."

It's Warren's populist streak that will play well even in red states, Marsh said, and that her tendency to tell it like it is has proven popular in a time of restrained politicians.

"She says what she means and she means what she says … damn the torpedoes," Marsh said. "People genuinely appreciate it and want more of it, frankly."

ABC News' Christopher Good contributed to this report.