As midterm primaries kick into high gear today, here are five signs (all Real Clear Politics averages) that the current headwinds for House Republicans could turn into a throw-out-members wave.

The bottom line: When a party is this badly under water in national sentiment and perception, individual candidates have a hard time distancing or distinguishing themselves. That's why a wave is apparent so early — 182 days before Election Day.

1. Congressional job approval: -56% (that is: 73% disapprove, 17% approve).
2. Approval of GOP tax cut: -7% (that is: 44% disapprove, 37% approve).
3. Direction of the country: -18% (that is: 55% of people think the U.S. is on the wrong track, 37% think the U.S. is headed in the right direction).
4. Trump job approval: -8 (that is: 52% disapprove, 44% approve).
5. Generic congressional ballot: Democrats +6 (that is: 45% of respondents say they'll vote for Democrats for Congress, 39% say Republicans).

The state of play: Today's primaries are in Indiana, North Carolina, Ohio, and West Virginia. Per The New York Times' election calendar, there are a number of competitive House races on the line. But much of today's news is likely to focus on the Senate:

• Three of those states have a vulnerable Democratic senator up for re-election (Joe Donnelly, Indiana; Sherrod Brown, Ohio; and Joe Manchin, West Virginia).
• And President Trump has already waded into the West Virginia primary, telling GOP voters that electing demagogic Don Blankenship would guarantee Manchin's re-election.

Go deeper: Why the Senate election map is so bad for the Democrats.