What would it take for you to vote for a Republican for, say, senator? Or be so disgusted with the alternative that you just wouldn't vote?
Probably the answer to that question depends on how likely it is that a single race can impact control, but these days the House, at least, is almost always up for grabs and obviously at the moment the Senate is too.
But really does it matter how "bad" a congressional candidate is as long as he mostly votes the "right" way? Sure it feels gross to reward bad people, but is that more important than whatever policy agenda they'll help to implement?
With realignment and Dems basically being Dems and Republicans basically being Republicans, at least in national offices, the so-called character issues, which drive much news coverage of elections, really don't matter all that much. Frankly, only sucker voters are swayed by them in most cases. I don't blame people for voting for Roy Moore, over and above blaming them for being conservative assholes generally. If you're a Republican you want Republicans to control the Senate.
This is much less true of executive positions than legislative ones, but not entirely untrue of them either.
The press prefers to cover "character" issues, even if they don't cover them well, because it's somehow less partisan, but, really, policy's the thing.
I'd hope the bad guys don't make it through the primary and the really bad guys somehow get removed from the ballot by the party if possible, but what would make me vote for Pat Toomey, really?