The Memo: Warren's rise is threat to Sanders

Senator Elizabeth Warren (D-Mass.) is on the rise in the battle for the 2020 Democratic nomination — and that spells trouble for Sen. Bernie Sanders (I-Vt.), her main competitor on the left.

Warren’s momentum was underlined by a CNN-Des Moines Register-Mediacom poll in Iowa over the weekend. It showed Warren just a single point behind Sanders, with 15 percent support to his 16 percent. The front-runner, former Vice President Joe Biden, led the pack with 24 percent support.

If Warren were to pull ahead of Sanders, she would become the...