Well, the actual revolution counts two "revolutions" (maybe even three if you count the revolution of 1905. Many historians do not count it as a revolution, but the Soviets loved to show it as one to prove that the people had always been against the government): The February Revolution and the October Revolution.

During the February Revolution the masses were the major player, lead by political opponents of the Tsar from all kinds of fractions (liberals, communists, social revolutionaries,...) That resulted in the Tsar abdicating and a provisional government being formed. Though, at the same time the Soviets (worker and soldier collectives) also assumed executive power. The Soviets did not officially deny the provisional government's authority, but it also ordered governmental orders by itself. There basically now where tow 'governments': the provisional government and the Soviets.

Lenin only got into Russia after the February Revolution. He realized the potential of the Soviets (which already counted many communist supporters) and managed to manoeuvre his Bolsjevists as the leading faction within the Soviets. Then, during the October Revolution, the Soviets took up arms and "stormed" (again an exageration by later Soviet historians) the provincial government's headquarters (the Winter Palace in St. Petersburg, if I'm not mistaken, but I can be wrong; don't take my word on that one), disbanded the government and took over St. Petersburg. So here, indeed, the Bolsjevists were the major players. Also the closing of the Constitutional Assembly that would later follow and that would lead to the Russian Civil War, was mostly the action of the Bolsjevist leadership.

The key players did the thinking, but I do not believe the revolution could not be possible without the masses. I've already written a response on a similar question here: http://www.reddit.com/r/AskHistorians/comments/2x4kkx/how_far_did_nicholas_iis_personality_contribute/. What I wrote definitely forms an answer to your question.

That's a divisive question, one that's kept schools of historians busy for decades. I'm going to give a quick overview of Western approaches to tackling the question and then spend a bit of time on why the popular image of a "few radical Marxists" is, in my mind, badly wrong. I'm not going to write a book on the subject though.

To simplify greatly, Western historiography on the issue can be roughly divided along three lines:

• The 'totalitarian' school focuses on ideology and political institutions to argue that these were captured in 1917 by, as you put it, "a few radical Marxists". This is probably best encapsulated by Richard Pipes' assertion in his (1990!) Russian Revolution that: "Nothing in early twentieth century Russia inexorably pushed the country towards revolution, except the presence of an unusually large and fanatical body of professional revolutionaries." At best such analyses stretch to include the supposed conservationism of the Russian people or pre-1917 political ideals. Pipes is the exemplar of this school.

• Fatalist or 'Menshevik' histories argue that while there was a genuine population and push for democracy in Russia, this was thwarted by the conditions in Russia at the time. Bolshevik popularity was either a manifestation of the country's backwardness or Lenin and co managed to fool the gullible masses and hi-jack the revolutionary movement. Think of the post-October memoirs by Mensheviks like Sukhanov or historians like John Keep and Orlando Figes.

• Then we have the 'revisionists'. This is a very broad term to describe the shift towards 'from below' studies of the revolution from the 1970s onwards. Broadly these historians reject the totalitarian thesis, emphasising the popularity and mass character of the Bolsheviks in 1917. Crucially, the workers and peasants are recognised as autonomous actors in their own right, rather than a backdrop to the 'grand politics' of traditional historiography. In this light Bolshevik popularity emerges as a product of their ability to advocate policies that chimed with the aspirations and identities of Russian workers. Examples of revisionist historians include Shelia Fitzpatrick, Alexander Rabinowitch and Moshe Lewin.

I'm not even going to try to present an even-handed evaluation as to which of the above is of the most value. As you can probably tell from the above, I'm squarely in the revisionist bracket, if only because it's a lot more nuanced than earlier efforts by émigrés or Cold Warriors. I find Pipes' theses to be absolutely unsustainable in the light of modern research. Instead I tend to agree with Allan Wildman when he writes, in Party, State & Society in the Russian Civil War, that:

the workers developed their own self-awareness, definition of goals and intensity of action, which, reversing the conventional equation, reshaped the Bolshevism of 1917. The Bolshevik Party succeeded in forging firm links to the working class in 1917 because it articulated and promoted this 'conciousness' more vigorously than its rivals, and in the process it reabsorbed something of the proletarian ethos.

This tallies with the picture of the Bolshevik Party as an "open mass party" (Fitzpatrick) that came to dominate worker organs - soviets, unions and factory committees - in 1917 because it was simply much more effective at talking to these same workers. In this, its open organisational structure (a far cry from Lenin's model of 'professional revolutionaries') and flexible ideology (again, far from the notion of rabid Marxists) were key assets.

None of this comes across from Pipes. To argue that October 1917 was a coup by a small cabal of radicals is to completely ignore the mass nature of 'Bolshevism' in October, the strength derived from close interaction with the masses of workers and the degree to which the Bolshevik Party itself differed from its supposed theoretical model of a small dedicated organisation.

In this regards, Sukhanov put his finger on the strength of Bolshevik power when discussing the attempts to defend Petrograd during the Kornilov Affair:

The [Committee for Struggle Against the Counter-Revolution] had to mobilise the worker-soldier masses. But the masses, insofar as they were organised, were organised by the Bolsheviks and followed them. At that time, theirs was the only organisation that was large, welded together by an elementary discipline, and linked with the democratic lowest levels of the capital. Without it the committee was impotent. Without the Bolsheviks it could only have passed the time with appeals and idle speeches by orators who had lost their authority. With the Bolsheviks the committee had at its disposal the full power of the organised workers and soldiers.

Does this sound like the reach of a "few radical Marxists"?

(In terms of sources, this obviously pulls from quite a few general works. Let me know if you'd like some recommended reading.)