Having won DC's 16 delegates and at least 28 of Maryland's 37 delegates tonight,* Romney now has 616 delegates, if we use the AP's count coming into the night. That's 57.4% of all delegates.
In order to get to the threshold of 1,144 delegates, Romney has to win only 528 of the remaining 1,213 delegates -- or 43.5%. Put the other way around: the non-Romneys have won 42.64% of all delegates to date, and in order to block Romney from winning before the convention, they would need to win 56.6% -- an improvement of 32.6%.
That's a very unlikely climb, especially when you consider that Utah is a winner-take all state with 40 delegates. So, if you take Utah off the table, the non-Romneys need to improve their performance by 37% over what it has been.
It's hard to consider this still a nomination fight.
*Looking now at Maryland results, Romney has huge leads (more than 50% more votes than Santorum) in all 8 congressional districts, meaning he'll get all 37 of Maryland's delegates, meaning taking Utah off the table, the non-Romneys would need to improve by 39.4% to block him from 1,144.