Romney, McCain, and the long slog to 1,144

[Important updates below]

I've written a bit previously (here and here) about how Romney has been doing in this year's presidential nomination contest compared to how McCain did in 2008. One thing that makes it difficult to compare the two years is that the current calendar is so backloaded; more than half the delegates in 2008 had already been awarded by the first week of February. We're still not at that point in the 2012 cycle, and it's almost spring. But here's one way to compare them: Below, I've charted McCain's and Romney's delegate shares compared to the total number of delegates that have been awarded to date. So, for example, by the time 1,247 delegates had been awarded in 2008 (Super Tuesday), McCain had won 740 of them. (I've used RCP's estimates of delegate shares in 2008 and 2012.) I've projected a linear path for both years.

So the big thing to note here is that Romney is accumulating delegates at a slower pace than McCain did four years ago. Also of note: Romney will not get to 1,144 delegates (a majority) by the end of the primaries and caucuses assuming he keeps accumulating delegates at his current pace.

Now, some very important caveats. (Speaker Gingrich, if you're reading this, you have enough to work with already, but the rest of you should keep reading.)

• The two years are still very different. Note that huge jump in McCain's delegate share between acquiring just over 100 delegates to acquiring over 700 of them. Remember, more than a quarter of all the delegates that would be awarded in 2008 were given out on Super Tuesday. We don't really know what McCain's delegate shares would have looked like had delegates been awarded on a more staggered basis as they are this year.
• Relatedly, due to the slower pace of delegate contests, few candidates have seen fit to drop out. McCain's dominance on Super Tuesday made it clear that no other candidate could win, and Romney dropped out at that point in 2008. Huckabee still won delegates in the South, but his campaign was essentially over by that point. If Romney had gone 12 for 20, instead of 6 for 10, on Super Tuesday 2012, it probably would have led to greater pessimism for Santorum and Gingrich. But there was no such day this year.
• In a different year, Gingrich probably would have dropped out by now. Only the recent advent of the Super PAC has made his ongoing campaign a possibility. And if he weren't in it, Romney would be acquiring delegates at a quicker pace. (See Josh Tucker's important post on this topic.)
• There's no real reason to believe Romney will continue to acquire delegates at this same pace this year. Romney looks likely to do well in Illinois tomorrow, as well as in some large winner-take-all states like New Jersey and California* later on. (And I like him for the winner-take-all Utah primary.) [*Note: California's primary is winner-take-all by state and congressional district. Thanks to Josh Putnam, Thomas Lavin, and DemConWatch for catching that.]

So my expectation is still that Romney will have this thing wrapped up before the primaries and caucuses are over. But it may take some time -- NJ and CA aren't until June 5th.

Update: Samuel Minter makes the very important observation that there are different total numbers of Republican delegates in 2008 and 2012, making a direct comparison of raw delegate counts misleading. I don't have a good excuse here. Anyway, I went ahead a changed the raw counts to percentages and produced... almost exactly the same chart:

I'm not really sure why his chart looks so different from mine. Perhaps it's because he's using Green Paper numbers rather than RCP numbers, perhaps because I use a linear projection and he doesn't....

Further update: Here's the chart post-Illinois. Romney's slope has increased ever so slightly.