To verify the claim, I sorted the states into R’s and D’s and then got the average % change for each group.
The R’s averaged a gain of +0.44%
The D’s averaged a gain of +16.60%
The R’s had 12 that were reductions and 14 that were increases.
The D’s had 10 that were reductions and 16 that were increases.
The R’s had fewer states than the D’s that saw reductions (10 verses 12) but also fewer states that saw increases 14 verses 16. In terms of numbers of states that did better, or not, the difference there is not so great.
It is on the percentages of the increases where the D’s made the biggest difference.
Maryland may have a Republican (Trump-hating RINO) governor but the state is deep red. His nickname in some quarters is "Lockdown Larry" and he is one of the current darlings of the propaganda media because of his animosity to PDJT.
I think this is correlation without causation. The party in power didn’t have anything to do with a medical event of 2 month duration.
The reaction and its economic effect will however. It will be interesting to see how Wolf in Pa. will explain his lockdown strategy when Pa. had the biggest reduction in deaths both in percentage and absolute numbers. Covid was a non-event in mortality in Pa.