Speaking at the U.S. News & World Report’s Healthcare of Tomorrow conference in Washington, D.C., former Senate Majority Leader Tom Daschle said, “I don’t see Medicare for All being a political reality anytime in the future.”

The concept of a single-payer, government-run system akin to those used in other industrial countries has become a virtual litmus test among the progressive wing of the Democratic Party. It has dominated the early debates among the nearly two dozen candidates seeking the party’s 2020 nomination.

Medicare for All was once considered a fringe issue but has soared into prominence, with both Sens. Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts making it a central feature of their campaigns.

The proposal, championed by Sanders, does away with private insurers as well as payments like premiums, copays and deductibles. However, while polls show Americans want more access to health care at lower costs, they also show many voters are wary of a complete takeover by the government.