In the U.S., we have historically had what American political scientists theorize is the "Rally 'Round the Flag" effect.
This U.S. political science theory purports that with every U.S. President who has experienced a domestic or foreign military crisis, action, or war - there has been an initial bump in approval ratings.
Thus far, this theory has been a reliable predictor of re-election.
However - note that Trump's initial and current aggregate approval ratings (RealClearPolitics, the one candidates themselves use) have actually dropped since the COVID-19 outbreak - and this week shows his lowest aggregate approval ratings yet ...
Note the number of red minus figures, indicating a negative change, even at publications that usually are "in the black," or indicate positive stability or positive change for Trump - to include Fox News polls.
Being that emergency war powers are being invoked, though - who knows?
Still, not good news for Trump regardless - and possibly 1 of the 3 reasons (see below post ) he conceded power to the governors?
(Because we all know how obsessed he is with his popularity;).