If Richard Blumenthal has to be replaced as the Democratic Senate nominee in Connecticut the party should still be favored to keep the seat as long as it gets a functional candidate.
In early January we polled Congressman Chris Murphy against Rob Simmons and Linda McMahon and he led each of them by seven points. Almost half of the voters in the state said they had no opinion of Murphy personally so he functioned basically as a generic Democratic candidate. If the nominee ends up being someone of comparable quality- or Murphy himself- the party will continue to be favored in the race although certainly not by the stratospheric kind of numbers that Blumenthal was.
And of course Blumenthal may be able to weather this- it's always hard to tell with these things.
Here's the numbers from our January poll