Pittsburgh (AFP) – President Joe Biden’s Democrats picked up a key US Senate seat in swing state Pennsylvania, boosting their chances of retaining their razor-thin majority in the upper chamber of Congress. Media projections early Wednesday showed John Fetterman, the state’s lieutenant governor, defeated celebrity doctor Mehmet Oz, a Republican who had the endorsement of former president Donald Trump. It has been one of the most heated and closely contested races of the US midterm elections. Fetterman, who is recovering from a stroke he suffered during the campaign, will take over the post vac…