The Clinton campaign has accused Russian President Vladimir Putin of leaking stolen Democratic National Committee emails to help Donald Trump's candidacy. Questions about Russia's involvement in the DNC hack loomed over the Democratic convention.

While the Republican presidential nominee has denied any ties to Russia, his connections to the country and its president go back years. Trump has talked about Russia being a hot business climate, and he has been trying to bring his brand to Moscow for decades, reports CBS News correspondent Julianna Goldman.

Most Americans might not know Russian pop star Emin Agalarov, but at the end of a 2013 music video is a scene that looks very familiar: a cameo from Trump sitting in a boardroom.

"What's wrong with you, Emin?" Trump asks in the video. "I'm really tired of you. You're fired!"

Agalarov is the son of Russian oligarch Aras Agalarov, a Vladimir Putin ally who is worth, according to Forbes, $1.3 billion.

The Agalarovs run the Crocus Group, a Russian real estate development firm that helped bring Trump's Miss Universe pageant to Moscow.

"You look at what's going on in Russia, in Moscow, you look at how it's just booming and how well it does," Trump said in November 2013.

The 2013 pageant remains Trump's most successful venture in Russia. When he returned to the U.S., he said he had a relationship with Putin.

"I spoke indirectly and directly with President Putin, who could not have been nicer," Trump said during a National Press Club luncheon in May 2014.

Nearly three years later, Trump changed his tune.

"I've never met Putin. I don't know who Putin is," Trump said Wednesday during a campaign event in Florida.

Over the last decade, the tycoon has had at least three potential real estate developments in Russia, but those plans never got off the ground. In a 2007 deposition, he spoke about plans for a Trump International hotel in Moscow and meetings with Russian businessmen.

"It's ridiculous that I wouldn't be investing in Russia," Trump said in the deposition. "Russia is one of the hottest places in the world for investment."

On Wednesday, however, he denied having business dealings there: "I will tell you right now, zero. I have nothing to do with Russia."

But Russians have bought Trump condominiums and partnered in Trump developments in Manhattan and Fort Lauderdale. Those deals were partially financed by the Bayrock Group, which has connections to private Russian money.

"Wouldn't it be nice if we actually got along, as an example, with Russia? I'm all for it," Trump has said.

Trump's financial disclosures do not show any Russian assets or investments.

But that hasn't stopped the Clinton campaign from making an issue of his Russian connections, from his stated fondness for Putin and policies that would empower the Russian leader to advisers who have made millions from Russian oligarchs -- like campaign chairman Paul Manafort, who worked for Viktor Yanukovych, the ousted Ukrainian president and a close Putin ally.

Manafort has denied Trump has any financial ties to Russia.

"So to be clear, Trump has no financial relationships with any Russian oligarchs?" Norah O'Donnell asked Wednesday.

"That's what he said. That's what -- that's obviously what our position is," Manafort responded.

Putin, it seems, is also fond of Trump.

"He is a very vivid man, very talented, no doubt about that. But this is not up to us to decide if he is worthy, it is up to the voters in the United States," the Russian leader said last December.

WikiLeaks is threatening to release more damaging information that the U.S. says it may have acquired from the Russian hackers. Any further leaks could fuel speculation that Putin is trying to help Trump win the election and raise questions about Trump's financial ties to Russia. Many of those questions could be answered if Trump released his tax returns.