It's generally accepted conventional wisdom that if your Senate candidate does well, then his or her coat tails will help the people running for Congress in the state. To find out if this was true, I looked at the last two wave mid-term elections. I set aside Presidential elections, because we wouldn't know if it was the Senator or Presidential candidate who was helping, and there is evidence that a President can have coat tails. By using the 1994 and 2006 elections, we'll have two elections which likely will closely resemble this year's election. In 1998 and 2002 not many seats changed hands. So there likely weren't coat tails. I included all the House seats that were believed in play or the elections were close.
The Democrats didn't lose any seats in the 2006 election, but the Republicans did lose four in 1994. So they were included as part of the study.
The two worst success rates for House seats were when the wave party (GOP in 1994 and Dems in 2006) won by between 20-30% and 10% or less. So overall, winning the senate race was the least likely path to win a House seat in play. I think the numbers are so close to each other that we can't say that a senate race helps congressional candidates or hurts them. I'm sure that in some cases the senate race did help them and in some cases it may have hurt. That's certainly arguable, but there's no way of knowing which ones a Senator will impact and which he won't. A big win in Arizona for McCain might not mean any of the three close races there goes Republican, while two New York Senate losses might not prevent the Republicans from picking up congressional seats.