As 2020 race heats up, growing worries Warren and Sanders will split leftist vote

At rallies at the Iowa State Fair last week, 2020 White House contenders Elizabeth Warren and Bernie Sanders drew raucous crowds who chanted their names, waved signs and cheered at their every pledge.

Friends and liberal standard bearers of the Democratic Party, the two U.S. senators espouse many of the same causes: universal healthcare, taking on Wall Street, and raising the minimum wage.

Both candidates also have robust, well-funded campaigns and strong claims on this state, which holds the first Democratic presidential nominating contest in February.

That has some voters...