This also has Biden winning by 7%, so yet another poll showing Peters underperforming the Democratic nominee for president by 3 points.
We saw this a lot in 2016. Ross, Murphy, Duckworth, Feingold, Cortez-Masto, Barksdale, Hassan, Judge, Strickland, and McGinty all underperformed Hillary. Bayh, Gray, and Kander were the only ones to outperform her.
But was it more that the Democrats underperformed Hillary, or that the Republican candidates overperformed Trump? The latter is definitely true with Rubio, Portman, Grassley, Toomey and Isakson at the very least.
Plus if we go back to 2012, Nelson, McCaskill, Manchin, Tester, Heitkamp, Brown, Kaine, Menendez (!), Stabenow, Carmona, Casey, and Kerrey all did better than Obama to varying degrees, so it's not always that Democratic Senate candidates do worse than the presidential nominee.