The provided article content consists only of the Daily Mail's website navigation, headline links to unrelated stories, and page furniture — the actual body text of this report was not included in the material supplied. As a result, no substantive details about the specific Republican Senate candidate, the state involved, or the nature of the "toxic" issue referenced in the headline are available to summarise accurately.

Based solely on the headline, the piece appears to concern concern within Republican circles that a particular political issue could damage a party candidate's chances in a competitive Senate race, with unnamed party figures reportedly worried internally. Without the full article text, further specifics such as names, polling figures, or the exact issue cannot be reliably reported.