What districts would the Republicans stand a better chance of beating the Dem contender by recruiting a stronger candidate (by which I assume you mean more conservative)? Do you really think Dems are going to vote Conservative? I dont think so. Dont you think if there is a RINO in office now its because a Dem would have won the seat otherwise...that there arent enough conservatives in the district to win, just enough to fight the good fight and lose.
And I didn't say a stronger candidate was necessarily more conservative. Note that many of the candidates in trouble---or, perceived to be in trouble---are liberal, many are conservative. It depends on the district.
It's just that the whole perspective of the WaPo is never that "Republicans could be even stronger" but always Dems "lost" the seat, never Republicans "won" it.