Speculation about a Hillary Clinton-Elizabeth Warren ticket has long swirled around the campaign, especially after Warren decided to not pursue a presidential run of her own. | AP Photo Clinton: Warren is 'qualified' to be my VP In an interview with POLITICO, Clinton says she has the 'highest regard' for the Massachusetts senator. But she didn’t say the same about Bernie Sanders.

Hillary Clinton on Thursday said she has no doubt that Sen. Elizabeth Warren would be qualified to serve as her vice president — but she refused to say the same of Bernie Sanders.

"I have the highest regard for Sen. Warren," she said in an interview with POLITICO. "I think she is an incredible public servant, eminently qualified for any role. I look forward to working with her on behalf of not only the campaign and her very effective critique of Trump, but also on the issues that she and I both care about."


Clinton appeared less open to the idea of Sanders as vice presidential nominee. "I think he has contributed greatly to the campaign," she demurred when asked if he had earned a place on the ticket. "His passions for the issues that he promoted has been good for the Democratic party and for the country. I look forward to talking with him when our campaigns can find a time that works with both our schedules."

Many Democrats from the more progressive wing of the party have fantasized about a Clinton-Warren ticket, and Clinton operatives have said they would be open to a two-woman ticket. But Clinton and Warren do not share a particularly close bond.

The progressive senator, whose political stature has quickly risen during the Obama administration, is expected to endorse Clinton Thursday evening.

A number of Warren's Senate colleagues — including Minority Leader Harry Reid — have been touting the Massachusetts senator as a unity pick for vice president. But some Clinton allies such as Ed Rendell, the former governor of Pennsylvania, have urged against Warren as a No. 2. "I think she will not pick somebody that she feels in her heart isn't ready to be president or commander-in-chief. I think Elizabeth Warren is a wonderful, bright, passionate person, but with no experience in foreign affairs and not in any way, shape or form ready to be commander-in-chief," Rendell said in a radio interview earlier this week.

Warren, whose office declined to comment, has maintained she is happy in the job she currently has in the Senate. She confirmed the stance again to reporters in Massachusetts this weekend.

A focus group conducted in January 2015 by pollster Peter Hart in Aurora, Colorado, offered some insight into how Warren might play as a national candidate. Among 12 voters — a mix of Democrats, Republicans, and independents — Warren was the one potential presidential candidate six of the 12 polled wanted to have over to their house to talk, more than any other presidential candidate.

In her home state, Warren enjoys high favorability ratings: 62 percent of Massachusetts voters approved of Warren’s job as senator, according to an April 2015 survey by the Western New England University Polling Institute. But she remains an unknown entity to 42 percent of the country, according to online pollster YouGov in April — essentially the same number as in a March 2015 NBC/Wall Street Journal poll that found 43 percent had no opinion or had not heard of Warren.

“The numbers were remarkably steady last year among swirling headlines and speculation whether she was going to run for president herself,” said nonpartisan pollster Steve Koczela of MassINC Polling Group.

Warren’s limited name recognition flies in the face of the assumption that she is an well-known entity with a fixed brand.

“Picking Warren is not equivalent to putting Bernie Sanders on the ticket,” said Koczela. “Elizabeth Warren is not a perfect substitute for Bernie Sanders. She may get you things and groups that Sanders represents in the long run, but it’s not a one-for-one replacement.”

Nearly everyone in the current crop of Democratic vice presidential prospects faces a name recognition issue, including Ohio Sen. Sherrod Brown, Virginia Sen. Tim Kaine, Secretary of Housing and Urban Development Julian Castro, and New Jersey Sen. Cory Booker. Republican pollster Ed Goeas of The Tarrance Group notes national name recognition isn’t a concern campaigns usually take into account, often relying more on state-based polling to see where things stand for the potential candidate.

With any relative unknown entity, the burden is then put on the campaign to define its veep candidate before it’s too late.

“It cuts both ways,” said Cornell Belcher, former pollster for the Democratic National Committee and an alum of both Obama presidential campaigns. “Being relatively unknown is like being a blank sheet of paper. You have the opportunities to write and tell your story. She has a pretty darn good story to tell moderate and Middle America. Is she a firebrand? Yeah. But she has a pretty good story that Middle America can define her with.”

“The flip side of not being well-defined is you give your opponent the opportunity to define you,” Belcher added.

Donald Trump, who's engaged in a Twitter war with Warren, has already stepped up his criticism of the senator. Both on Twitter and in speeches, he's referred to her as “Goofy Elizabeth” and “Pocahontas,” a reference to her claim to Native American heritage that emerged as a major flashpoint in her contentious 2012 Senate race against then-Sen. Scott Brown.

Pollsters are split on the effect of her recent conflicts with Trump.

“She’ll be defined by Trump’s nicknames,” said Republican pollster Wayne Johnson.

“She’s being a good Democrat. She is taking Trump on really effectively, I think,” Belcher said.

Clinton assumed the mantle of presumptive Democratic nominee on Monday after she amassed enough delegate support, and President Barack Obama on Thursday forcefully endorsed her, saying, "I don't think there's ever been someone so qualified to hold this office."

Obama also met with Sanders for an hour at the White House on Thursday, after which the Vermont senator said he plans to stick in the race through next Tuesday's D.C. primary.

But he said he plans to sit down with Clinton next week to talk about the best way to defeat Donald Trump in the general election.

Lauren Dezenski contributed to this report.

