Viewed another way, this is an opportunity for Rubio. He can seize the moment as a chance to showcase himself as a stark contrast to the clear Democratic frontrunner and demonstrate to voters how he would stack up against her in a general election. It's a chance to look like he's leading the charge to prevent Clinton from getting elected.
The debate was in full swing on Twitter Friday morning. Rubio's aides retweeted observations from the this-could-be-good-for-Rubio camp:
Rubio’s announcement on Monday will now be a direct contrast with Hillary - Ideal set up for generational choice— Charlie Spiering (@charliespiering) April 10, 2015
At least one observer raised the idea of a "split-screen" moment, which could be good for Rubio:
I disagree w/ the notion that Clinton steps on Rubio rollout by announcing Sunday. A Clinton/Rubio split-screen on Mon & Tues elevates him— Garrett Haake (@GarrettHaake) April 10, 2015
Of course, there are plenty of people in the other camp too: