Julian Zelizer: The Real Race is on Between Romney and Obama

(CNN) -- Rick Santorum's announcement that he is suspending his presidential campaign brings the Republican primaries closer to the end. With all the speculation about brokered conventions and last-minute turnarounds, the original predictions appear to be correct. Mitt Romney will almost certainly be the Republican candidate who faces off against President Barack Obama in the fall.

The rebellion against Romney took on many forms since this primary season began. We saw the business conservative (Herman Cain), the ideological and slash-and-burn conservative (Newt Gingrich), the libertarian (Ron Paul), the movement conservatives (Rick Santorum and Michele Bachmann) all try to win the hearts and minds of Republican voters by claiming that they were better suited to this role than Romney.

But in the end Romney wins. We can learn a number of lessons from this outcome. The first is that organization and money do matter....