Yes, Tuesday 24 April was, indeed, a big night for former Massachusetts Governor Mitt Romney:
he swept all five Presidential Primaries held that day- in Connecticut, Delaware, New York State, Pennsylvania and Rhode Island and he did, in fact, "pile up" the lion's share of National Convention delegates up for grabs in said Primaries: 146 of the 150 available in all States outside of Pennsylvania and- so far, at least (difficulties with determining the pledges of 59 Pennsylvania delegates separately elected, delegates who could not indicate their actual preference for President on the ballot per se, being what they are)- he is assured of at least half of the delegates from the Keystone State and, likely, will pick up several more (as of this typing).
I myself had earlier opined that- had former Pennsylvania Senator Rick Santorum remained active in the race- Governor Romney gaining half [104, 105] of the 209 delegates up for grabs this past Tuesday would have been (albeit barely) acceptable, with 2/3 (around 140) acceptable: once Senator Santorum was out, 2/3 now became the minimum Romney needed to gain with more than 3/4 (which would have been over 157 delegates) on Tuesday being the optimum (I was, effectively, giving Romney something of a "hall pass" here because of Pennsylvania's use of the so-called 'Loophole'-type Primary [added to the fact that Pennsylvania, being Santorum's own home State, might have still given notable delegate support to the man who was now, in essence, its mere "favorite son" presidential candidate]: had the Keystone State been using a system through which delegate pledges were more directly related to the Presidential Preference voting in that State, I would- more likely- have thought more than 4/5  would have been the optimum for Romney this past Tuesday)...
well, Romney- by the very count I just provided a couple paragraphs back- gained the pledges of no less than 173-- that is: more than 4/5 of 24 April's 209!
But there is still much work for Governor Romney yet to do to unify the Republican Party around his presumptive Presidential Nomination: fortunately for him, he still has some four months before the Republican National Convention meets in Tampa in which to do it... yet Warning Signs abound, indicating that the acceptance of his presidential candidacy against President Obama this coming November is still not wholly acceptable to all to many to the right of center in the American political spectrum of 2012, both within and without the Grand Old Party itself.
True: former U.S. House Speaker Newt Gingrich is prepared to drop out of the contest (as of Tuesday 1 May, at last report): indeed, a former presidential contender who had once endorsed Speaker Gingrich- Texas Governor Rick Perry- has already endorsed Governor Romney (possibly a sign as to where Gingrich himself might well be prepared to go-- at least at some point!- once he has publicly abandoned his own quest).
But Rick Santorum has not yet endorsed Romney publicly!
A "summit meeting", of sorts, is now scheduled for Friday 4 May between Santorum and Romney-- and what comes out of that will go a long way towards answering the still-important question: 'how soon can Mitt Romney 'clinch' the 2012 GOP presidential nomination?'
For, as big as Romney's victories this past Tuesday were, they still pretty much occurred in what has to fairly be considered 'Romney-friendly' territory (and, here, the very vagaries of the scheduling of Presidential Primaries well came into play: for what if, say, the Great Northeast ["Gateway to America" ;-)] had already voted, earlier in the "season", in their respective Presidential Primaries while Santorum- and, for that matter, a more viable Gingrich- were still in the race and 24 April had, instead, been played out in another section of the country? Would there have been more of a so-called "protest vote" emergent or would Romney have done just as well? There is no way to really know, of course-- just as there is no way to know if Romney would have done just about as well- or not- in the five Primaries actually held on 24 April had Santorum not suspended his campaign two weeks before that?)...
yet: Newt Gingrich- while failing to win Delaware (the last hope onto which he and his candidacy could cling going into 24 April)- did get more than 1/4 of the vote in the First State: not as significant as it might otherwise have been, mind you, but still notable; and Rick Santorum did pick up some 18% of the preference vote in his own Pennsylvania ("protest vote"? or merely an honorific "sendoff" for the "favorite son" from many of his former constituents?)...
the next round of Presidential Primaries- those of Tuesday 8 May- take place in areas where, up till now, Governor Romney has had no little difficulty convincing the electorate: Indiana (Great Lakes State neighbor to both the Michigan [28 February] and Ohio [6 March] in which Romney had previously eked out victories; although it is also the neighbor of Illinois where- or so it can be argued- Romney may well have already begun to knock Santorum out of the race back on 20 March); North Carolina (a Southern State [the South, to date, has not been all that 'Romney-friendly']); and West Virginia (a State which- as journalist Joel Garreau pointed out in his book The Nine Nations of North America- tends to, in essence [for I'm paraphrasing Mr. Garreau here], be 'Great Lakes State' in good times, 'Southern State' in bad)...
if an 'anti-Romney' "protest vote" (one in which any such "protest voters" are effectively saying: 'OK, Mr. Romney-- we get that you're going to be the Major Party challenger to Obama in 2012-- but you're still going to have to work for it!') is actually going to emerge late in this 2012 Republican Primary/Caucus "season", it will first be seen in these 8 May Primaries-- if not so seen, Mitt Romney is then already well on his way to unifying his Party behind his presidential candidacy.
But there is still a veritable shadow now haunting Governor Romney (where not also the Republican Party itself) and it is that of Texas Congressman Ron Paul:
no, Congressman Paul is not going to be able to wrest the presidential nomination away from Mitt Romney, either before or during this year's Republican National Convention in Tampa-- but he and his more vociferous supporters seem determined to be heard from at that Convention and not at all "muzzled" as they were at the last Republican National Convention in St. Paul four years ago!:
this past Tuesday, Congressman Paul won nearly 1/4 of the vote in Rhode Island (along with 4 of the Ocean State's delegates)-- he was also in double digits in percentage in the presidential preference voting in the other four States that also voted that day... in addition, Paul has been recently gaining the pledges of "pockets"- as it were- of National Convention delegates in post-caucus higher-tier Conventions in States such as Minnesota.
These "pockets" of delegates are relatively small in number, to be sure-- but the Convention in Tampa having to, somehow, fit Ron Paul and his supporters into its usual "script" for that particular conclave scares the bejeezus out of not a few within the hierarchy of the Grand Old Party already planning for that Convention-- that of a GOP that is going to have to run, at least in part, on its own traditional sociocultural (in addition to politicoeconomic) conservatism in the General Election: a sociocultural conservatism that does not, in and of itself, all that well dovetail with the inherent libertarianism (including significant differences with mainline Republican geopolitics as well) of many- if not most- of Ron Paul's most ardent admirers and defenders (again, both within and without the Republican Party).
Newt Gingrich and Rick Santorum will both, almost certainly, endorse Mitt Romney's eventual nomination for President of the United States- later, if not sooner- but Ron Paul is already the last 'anti-Romney' Republican presidential candidate still standing and Paul's most loyal supporters, quite simply, "take no prisoners"...