President Trump’s slide in the polls since he tested positive for the coronavirus has Republicans newly worried about their control of the Senate, as even some races in what are supposed to be safe red states are beginning to appear competitive.

Incumbent GOP Sens. Martha McSally of Arizona, Susan Collins of Maine, Cory Gardner of Colorado, Thom Tillis of North Carolina, Joni Ernst of Iowa, and Lindsey Graham of South Carolina are all considered vulnerable. If Joe Biden wins the presidency, only three of those seats would need to flip for Democrats to capture the Senate, factoring in what would then be Kamala Harris’s tie-breaking vote as vice president.