According to that chart in the article, manufacturing activity stayed below 50 longer than the dip in 2012 (Obama’s reelection campaign), longer than the dip in 2016 (Hillary’s election campaign), longer than the dip in 2020 (Trump’s reelection campaign). Obama was still reelected (but had less electoral votes in 2012 than 2008), Hillary and Trump both lost their elections in 2016 and 2020. Yet Donna Brazile still claimed on yesterday’s This Week that Biden can point out that manufacturing is strong again. But this chart shows manufacturing is at a weak point now.
Well, not surprisingly Sanders is using out of date data. PMI is back above 50:
More to the point, PMI is really a survey of purchasing activity so it's more a forward looking indicator than a measure of current activity.
If you look at manufacturing employment it's been a pretty steady rise since the pandemic.