Influential Republicans in Washington and among the nationwide party elite are having a belated "oh s--t" moment over the previously unimaginable prospect that Kathy Barnette could win their party's nomination for the open Senate seat in Pennsylvania. Why it matters: In Barnette, who's been soaring in the polls ahead of Tuesday's primary, Senate Minority Leader Mitch McConnell would be dealing with a general election candidate who'd be an opposition researcher's dream — potentially endangering the GOP effort to take back the Senate. McConnell has been fixated on ensuring the 2022 midterms are not a repeat of the 2012 or 2010...