Editor's note: John Avlon is a CNN contributor and senior political columnist for Newsweek and The Daily Beast. He is co-editor of the book "Deadline Artists: America's Greatest Newspaper Columns."
(CNN) -- The message of Super Tuesday was clear: Mitt Romney still cannot seal the deal with the conservative base, despite winning six states and outspending his rivals 4-to-1. And while Romney is far ahead of his rivals with 404 delegates collected to date, he needs 740 more to clinch, a process that could take at least until May and possibly go all the way to the convention.
Rick Santorum's impressive 9-point win in Tennessee -- along with victories in North Dakota and Oklahoma -- further solidified his status as the conservative alternative to Romney.
Newt Gingrich scored a strong 20-point win in his home state of Georgia, but he came in third or fourth in all the other contests. There will be growing pressure on him to drop out of the race, which would allow a majority of his supporters to coalesce around Rick Santorum. But thanks to super PACs, Newt will have more than enough money to stay in the race and keep making his case.
Romney's razor thin 1% win in Ohio illustrates the problem facing the GOP. Romney won the urban clusters that tend to go Democrat in the general election. Rick Santorum's strength was in the rural areas that dependably vote Republican.
The economic gap was apparent, as well: Romney won voters making more than $100,000 a year, while Santorum won voters making less than that amount. Likewise, Santorum won voters who described themselves as "very conservative" on both fiscal and social issues, while Romney won self-described moderates and the somewhat conservative. Tea partiers and evangelicals went to Santorum, while non-tea partiers and non-evangelicals went to Romney.
These dynamics suggest that Romney might be the better general election candidate in terms of crossover appeal, but he still leaves the base cold.
Crucially, Romney had the edge in Ohio with women voters, who seemed to break with Santorum after social issues such as contraception dominated the debate instead of his previously winning message of the middle-class squeeze. And surprisingly, Romney beat Santorum among Catholics, despite his very public professions of faith.
Romney's base problems were revealed in the fact that he lost North Dakota to Santorum, despite winning the state easily four years ago.
But it was Virginia that perhaps best revealed the depth of anti-Romney sentiment. Because of arcane and frankly idiotic ballot access rules, Romney had the Virginia ballot all to himself with the exception of Ron Paul. The Libertarian congressman won just 4.5% of the Old Dominion State vote four years ago. This year Paul won 40%, while Romney cleared 60%. That almost tenfold increase provided Paul's best percentage showing of the night and served as a way of gauging just how committed some conservatives are to voting for someone other than Romney.
The GOP is now facing the prospect of a very long nomination fight. The next contests are in Kansas, Alabama and Mississippi - socially conservative states unlikely to be friendly to Romney. Moreover, the proportional nature of this primary contest means that unless the other candidates bow out -- something less likely than in years past given the single-donor super PAC infusions that can sustain a campaign -- this primary season will go the distance.
Consider the fact that if Romney were to win all the delegates going forward, he wouldn't clinch the nomination until May. And mathematically, it remains possible that Romney might not be able to clinch the 1,144 delegates necessary to avoid a contested convention.
All of this is something close to a worse-case scenario for Republicans. Romney can't deliver a knockout punch, but Santorum, Gingrich and Paul can deny him the nomination even if they can't win it themselves.
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The opinions expressed in this commentary are solely those of John Avlon.