It's not shocking that some Republicans are concerned about President Trump's re-election chances next November — polling, while early, suggests he's in for a real fight against former Vice President Joe Biden, and the country's struggles caused by the coronavirus pandemic have cast even greater doubt. But some members of the GOP are also growing more wary of the party's ability to hang on to the Senate, The New York Times reports.Recent surveys showed Republican senators in Arizona, Colorado, North Carolina, and Maine are vulnerable. If those seats are lost and the other 96 remain steady, Democrats would gain control of the upper chamber. Republicans could gain a seat back in Alabama, the Times notes, though if Biden wins the presidency, the pendulum would again swing back to the Democrats.Because those seats are likely tied to Trump's own performance, he'll need to "run very close for us to keep the Senate," Charles Black Jr., a veteran Republica...