Excuse me, this is fucking wrong. The only reason why Putin got power is because of his KGB roots, the oil price spike and the purge of opportunist oligarchs. The only reason why Putin/Medvedev duet remains in power is because they're the only competent political entity with a movement that has clear and stable agenda since they've been so long in power as a result of gaming elections.
There's not a lot of opposition for Putin since there's no criteria for a valid opposition to be formed. Those are:
1) A viable alternative. There's a grand total of three parties that are relevant, despite what ballot may say - LDPR, KPRF and United Russia, Putin's party. KPRF is a fucking communist party and as long as people remember what communism leads to (or rather, it's incompetence) it won't get a leading vote. LDPR is a different story - while it's supposed to be a liberal-democratic party it's anything but thanks to Vladimir Zhirinovsky, who made his reputation by being as scandalous as possible - CNN would have a field day with him. Every goddamn day of the week.
2) A clear, well defined game plan. So, there's two alternative parties, one communist and the other other maybe-sorta-better. So what's the problem? Go out and vote for LDPR/another independent candidate that happens to be better for the nation? Well, it's not that easy. Putin's presence in the foreign policy has allowed him to make very complicated decisions and his actions imply that he did everything he could to avoid being labeled as anything that's too broad a term, like liberal, conservative etc. Basically, he made several moves in internal and foreign policy that are long-term instead of short-term because their party is in power for too long and they know this. A new party comes in, there's no direction to head in, our new set of heads at the top fucks up a long-term agenda, we're screwed.
3) A movement to lean on. Unless there's a serious fault with the current administration and/or a serious benefit to a new administration, you're not gonna see any serious change. Russian people are like that, and it's not gonna change since the principle of "if it works, don't fix it" did not fail anyone yet. Unless there's a manufactured scandal with an evidence stacked about two Clinton's email stashes high, you're not gonna see dick and even then communists might try to use it to seize power. And then it's gonna be even worse.
4) Prevention of rigging. There's videos of ballot stacks dropped into ballot boxes on the internet. There's videos of United Russia propagandists going to Russian universities for recruitment on days when it's illegal to do so. Look it up, there's a lot more bullshit like that but it's real.
Therefore it is accurate to say that he and his party will remain in power because nobody cares enough to risk communism to happen to Russia again.