soft-pedal

To reduce the volume of (music, a sound, etc.).

To reduce the force or impact of (something); to damp, to mute; especially, to minimize the less desirable aspects of (something); to play down, to tone down.

But when the first female also-ran at a convention merits such hoopla and hosannas, then it is harder for viewers to understand why the Democrats seem intent on soft-pedaling their presumptive nominee's arguably more remarkable breakthrough.

To attempt to persuade someone about (something) through understatement, so that the listener accepts the good points as obvious.

Chiefly followed by on: to act in a less assertive or forceful manner.