In the latest example of the Russian authorities' widening censorship campaign ahead of State Duma elections, the country's Internet regulator has ordered the shutdown of an independent website aimed at helping voters learn about candidates.

The site, Duma.vote, is backed by Mikhail Khodorkovsky, the exiled oil tycoon who in recent years has stepped up his criticism of the Kremlin by funding and supporting opposition activists and independent media outlets.

At first glance, the website is devoid of any overt political messaging, or endorsements of candidates or blatant anti-Kremlin signals. "We are not encouraging you to vote in one way or another," the site says. "We provide information so that you can make an informed choice."

But the goal, the site says, is to help voters identify which candidates have stated they support having President Vladimir Putin stay in office beyond 2024.

The question of whether Putin will stay in office after his current term ends looms over the September 17-19 Duma elections -- and over all Russian politics for the next two years.

Last year, the State Duma, the lower house of parliament, backed a constitutional amendment that effectively removed term limits for Putin, allowing him to run for reelection in 2024 and 2030.

Putin has not announced whether he will seek to stay in office. If he does, or if the Kremlin seeks to restructure the country's executive powers and find a way to keep Putin as the preeminent political leader without being president, it will need a compliant Duma to provide legal cover.

The Duma.vote website does argue the amendments removing term limits were unconstitutional. "The unconstitutional extension of the office of the current president, for which he had to go to the destruction of the country's Basic Law, will allow Putin to stay until 2030, or even until 2036," the site says.

In banning the site, the Internet regulator Roskomnadzor cited an existing law that allows for websites, online media, and even more routine printed media to be blocked if they are deemed to promote "mass disorder or extremist activities." The law also empowers the regulator to censor information or sources that it deems to be unreliable.

In the run-up to the Duma vote, authorities have targeted a range of media and information sources. Among them are websites linked to Aleksei Navalny, the jailed anti-corruption lawyer who has spearheaded the Smart Voting initiative. That initiative aims to guide Russian voters to vote for candidates who have the best chance of beating a candidate from the dominant ruling party, United Russia.

This year, Navalny's allies built an app to make it easier to guide voters. But officials have sought to block any websites promoting Smart Voting and have asked tech giants Apple and Google, as well as Russian search engine Yandex, to remove the app from its stores.

Officials have tried to block local servers that help facilitate app purchases, and also gone after providers of Virtual Private Networks (VPNs) -- services that help hide a user's online identity and circumvent restrictions. This week, the country's communications regulator even sought to block website security providers, in an effort to shut down access to the Smart Vote app.

For his part, Khodorkovsky has seen a number of non-election-related projects blocked or targeted by prosecutors.

In August, news sites Open Media and MBK Media closed down after Roskomnadzor blocked their websites, as did a human rights group called Pravozashchita Otkrytki. Two activists currently or formerly affiliated with Khodorkovsky-linked projects have been prosecuted; several reporters for the news sites have been hit with "foreign agent" designations under Russian law.

"What else is here to say?! This is self-explanatory," Maria Logan, a Khodorkovsky spokeswoman, said in an e-mail to RFE/RL. "If you are an activist, independent journalist or simply someone who is critical of the way Kremlin runs the country, you have a choice of exile, prison or working with a label of [foreign] agent which in practice means you are a spy and a traitor. The scare tactic works."

"But many also find a way to adapt to this very challenging situation and continue their fight against the rogue regime," she said.