Gallup:

Gallup's annual Governance survey shows that trust in the federal government has continued to decrease this year after showing noticeable signs of decline the past two years. Now, Americans generally express less trust in the federal government than at any point in the past decade, and trust in many federal government institutions is now lower than it was during the Watergate era, generally recognized as the low point in American history for trust in government.

Both the legislative and executive branches share the blame:

[T]he 43% who now express trust in the executive branch is only slightly better than the 40% who did so in April 1974, four months before Richard Nixon resigned as president amid the Watergate scandal.
. . .
Trust in the legislative branch of the federal government continues to erode, dropping six percentage points in each of the last two years (from 62% in 2005 to 50% today). The current level of trust in Congress is significantly lower than any other measurement Gallup has obtained.

More findings here.