CLINTON, Iowa (Reuters) - Elizabeth Warren has recalibrated her rhetoric on Medicare for All, as concerns about her support for replacing private insurance with a government-run plan continue to buffet her once-surging Democratic presidential campaign.

FILE PHOTO: Democratic 2020 U.S. presidential candidate and U.S. Senator Elizabeth Warren (D-MA) delivers a campaign economic speech at Saint Anselm College’s Institue of Politics in Manchester, New Hampshire, U.S., December 12, 2019. REUTERS/Brian Snyder

During a three-day, seven-stop tour of Iowa last weekend, the U.S. senator from Massachusetts repeatedly emphasized the word “choice” and focused on the transition plan she unveiled last month that would delay full implementation of the sweeping healthcare overhaul for three years.

“It’s your choice if you want to come in and get full healthcare coverage,” Warren told about 180 people at a community center in Clinton, Iowa.

The state holds the first nominating contest in the country on Feb. 3 for Democratic contenders seeking to run against Republican President Donald Trump in November 2020.

The message is part of Warren’s closing argument as she seeks to cement her status as a front-runner among the 15 Democrats pursuing the party’s nomination.

But it remains to be seen whether that will be enough to ease some voters’ minds in Iowa, where the more moderate former Vice President Joe Biden and South Bend, Indiana, Mayor Pete Buttigieg have moved past Warren in opinion polls.

Colleen McDevitt, a middle school staff associate in Dewitt, Iowa, is leaning toward supporting Warren but said she is “still kind of iffy” on her healthcare proposal.

“I kind of lean toward having a choice,” McDevitt said while awaiting Warren’s arrival in Clinton.

Both Biden and Buttigieg have criticized Warren over Medicare for All, with Buttigieg in particular arguing that his proposal to offer a government-run plan alongside private options is the only way to preserve “choice” for Americans.

Warren’s decision to highlight her transition plan appears aimed at defanging Buttigieg’s attacks. But it has also drawn grumbling from some supporters of another leading rival, fellow liberal U.S. Senator Bernie Sanders of Vermont, that she has backed down on the issue.

Warren told reporters in Iowa she was simply explaining her plan and dismissed comparisons between her proposal and Buttigieg’s, which she said was less comprehensive and more costly for families.

Buttigieg campaign spokesman Sean Savett said the mayor’s plan would offer universal, affordable coverage.

“The difference is Pete’s plan also preserves health care choice for all Americans,” he said. “It’s a difference not just in policy, but in approach to governing.”

The issue will likely arise on Thursday at the latest Democratic debate, where Warren, Buttigieg and Biden will share the stage with four other top contenders.

CHANGING TACTICS

Warren’s campaign has made other tactical alterations in a bid to revive its momentum.

She has slashed her stump speech from around 45 minutes to 10 to answer more audience questions - the former law professor fielded nearly 70 between Saturday and Monday. She has more aggressively criticized Buttigieg and Biden, though usually not by name, for their ties to wealthy donors, while noting she has sworn off high-dollar fundraisers.

Starting with a speech last Thursday in New Hampshire, Warren has also sought to return to the overarching themes of anti-corruption and economic populism that helped lift her campaign throughout the summer.

In answering questions on everything from pollution to mental health, Warren returned again and again to her plan to tax the super-rich – including a wealth tax – to pay for a host of ambitious programs, including universal child care, student loan debt cancellation and tuition-free higher education.

But she has continued to face persistent queries from voters on healthcare, including those who believe she is right on the issue but might pay the price in an election against Trump.

“I’m a fan of your Medicare for All plan, but I keep hearing from people who are afraid, A, of the cost, and B, that they’re not going to be able to ... see the doctor they want,” Camille Anderson, 54, said in Keokuk, Iowa.

Warren explained how she would finance Medicare for All through new taxes on the wealthy and corporations and again told voters they would have a “choice.”

Afterward, Anderson said Warren must find a more compelling, concise argument to win over skeptics.

“I think that question is going to keep plaguing her,” she said. “Not everyone is going to be willing to delve into the details.”