Speaker Nancy Pelosi is guiding House Democrats along a narrow path as she seeks to convince party progressives that the idea of providing Medicare for everyone in the U.S. is being taken seriously, while assuring moderates that the House won't move too far, too fast.

The House on Tuesday will gavel in the first-ever hearing on a sweeping Medicare for All proposal, an idea that's energized the Democratic left, which is pushing to make it a central part of the 2020 campaigns for the White House and Congress.

If private health insurers are one day put out of business by a government-run single payer health system, they may look back at Tuesday as the beginning of the end. Yet the bill coming before the House Rules Committee won't become law anytime soon and may never get a hearing in the committees that oversee Medicare.