Russia's Recurring Role in the 2016 Presidential Campaign

— -- The controversy surrounding one of Donald Trump's top campaign aides and his alleged ties to a pro-Russian Ukrainian party is just the latest development in an ongoing saga.

Trump's seeming closeness — personally and in terms of policymaking — with Russian President Vladimir Putin has been an issue throughout the campaign.

Here is a rundown of Russia's role in the 2016 presidential campaign, as well as various statements Trump has made about Putin.

Accepting and Giving Compliments

When Trump was asked in December about reports that Putin was cracking down on internal dissent by killing journalists and political opponents, Trump's response seemed complimentary of Putin.

"He's running his country, and at least he's a leader, unlike what we have in this country," Trump said.

And when Putin described Trump as a "bright and talented person," Trump released a statement through his spokeswoman Hope Hicks that said, "It is always so great to be so nicely complimented by a man so highly respected within his own country and beyond."

Approval of Putin's Annexation of Crimea

In a late July news conference, Trump said he "would be looking at" the possibility of lifting sanctions against Russia tied to its illegal annexation of Crimea — which the U.S. government refuses to recognize.

"He's not going into Ukraine, OK, just so you understand. He's not going to go into Ukraine, all right? You can mark it down. You can put it down. You can take it anywhere you want," Trump told George Stephanopoulos during a subsequent interview for "This Week."

When Stephanopoulos said, "Well, he's already there, isn't he?" Trump tweaked his answer, blaming the current situation on President Barack Obama.

"OK, well, he's there in a certain way. But I'm not there. You have Obama there. And frankly, that whole part of the world is a mess under Obama, with all the strength that you're talking about and all of the power of NATO and all of this. In the meantime, he's going away. He take — takes Crimea," Trump said.

Trump defended his tweaked explanation at a rally in Columbus, Ohio, on Aug. 1 and didn't shy away from suggesting improved relations with Russia would be a good thing.

"First of all, I have to say this. Wouldn't it be great if we got along with Russia? Am I wrong in saying that? Wouldn't it be great?" Trump said at the rally.

He continued, "Putin said some very good things about me. People say, 'Oh, Trump's going to be weak with Putin because Putin is saying nice things about me.' OK, all right. And I said he's a strong guy. They immediately say, 'Oh, Trump likes Putin.' Look, I don't like or dislike. I just say this way, wouldn't it be great if the United States and Russia got along, combined, knocked out ISIS, maybe did other positive things?"

Their Meetings – or Lack Thereof

There have been at least three times from 2013 to 2015 that Trump said he has met or spoken directly or indirectly with Putin.

But now Trump says they've never met or spoken.

During an interview with ABC, Trump said, "I have no relationship with him." But he went on to say, "Well, I don't know what it means by having a relationship."

"I didn't meet him. I haven't spent time with him. I didn't have dinner with him. I didn't go hiking with him. I don't know — and I wouldn't know — him from Adam, except I see his picture and I would know what he looks like," Trump told George Stephanopoulos in an interview for "This Week."

That comes in clear contrast to Trump's comments in 2014 at the National Press Club, when he said, "I was in Moscow recently, and I spoke, indirectly and directly, with President Putin, who could not have been nicer."

The Democrats and the DNC Hack

Not only are questions about Russian interference being raised in terms of the Trump campaign, but also security experts pointed to Russian hackers behind the Democratic National Committee email hack.

The hack and the contents of some of the emails led to the resignation of Debbie Wasserman Schultz as DNC chairwoman.

Hillary Clinton's campaign chairman, John Podesta, said the suggested ties between Russia and the hack are "very worrisome."

"Whether they're actively trying to interfere in the U.S. election, that's something that I guess we'll need to see," he said.

Trump speculated in a speech after the hack that "China, Russia or one of our many, many friends … hacked the hell out of us," but the GOP candidate and his top advisers have rejected the suggestion that the Russians were motivated to help the business mogul.

In a later tweet, Trump wrote, "The new joke in town is that Russia leaked the disastrous DNC [emails] … because Putin likes me."

Manafort's Alleged Money Trail

Trump's questioned friendliness with Russia isn't the only possible connection between his campaign and the country.

Trump's campaign chairman, Paul Manafort, advised Ukrainian President Viktor F. Yanukovych during his election campaigns before he was ousted in 2014. Yanukovych was a Putin supporter.

Manafort’s connections to Yanukovych and his party have surfaced intermittently over the past decade, first attracting notice during the 2008 U.S. presidential campaign when Manafort's partner in his firm, Davis Manafort Inc., was found to be advising John McCain at the same time as the firm appeared to be working to improve Yanukovych’s image abroad. As the Wall Street Journal reported then, Department of Justice filings showed that Manafort’s firm had hired a PR company in Washington to lobby on behalf of Yanukovych’s Party of Regions. The filings describe a firm owned by Manafort as being “directed by a foreign political party, the Ukraine Parties [sic] of Regions to consult on the political campaign in Ukraine.”

According to the filing, the PR firm, Daniel J. Edelman, Inc., was tasked with creating “a communications campaign to increase Prime Minister Yanukovych’s visibility in the U.S. and Europe” and to communicate “his actions toward making Ukraine a more democratic country.”

The Wall Street Journal reported again in 2010 just after Yanukovych won an expected return to the presidency that members of the Party of Regions credited Manafort with the victory.

Manafort himself at the time refused to comment on this or other reports that he was advising the Ukrainian president.

Manafort's international work gained scrutiny this weekend when The New York Times reported that his name appears on a list of off-the-books payments amounting to $12.7 million from 2007 to 2012.

He has since denied the reports, but the Ukrainian Anti-Corruption Bureau confirmed that his name appears in a ledger of payments, though it is still investigating whether the money was delivered to him.

Manafort released a statement saying he "never received a single off-the-books cash payment as falsely reported by The New York Times, nor have I ever done work for the governments of Ukraine or Russia."

"The suggestion that I accepted cash payments is unfounded, silly and nonsensical," he continued.

He added that his work in Ukraine ceased after "the country's parliamentary elections in October 2014."

During an earlier interview, he was asked by ABC News if there were any ties between Trump's campaign and Putin, and Manafort denied it unequivocally.

"No, there are not. That's absurd. And you know, there's no basis to it," he said.

Another Adviser's Connection

Manafort isn't the only person with access to Trump who has a connection to Russia.

Carter Page, an energy expert Trump tapped as a foreign policy adviser, spent three years living in Moscow working on key transactions with Gazprom, a Russian oil giant that is largely state owned. Page was in Moscow last month to give a speech at a Russian business school.

Trump has explored the real estate market in Russia as far back as 1990 and toured Moscow with close friend and real estate developer Howard Lorber.

Lorber doesn't have a formal role in the Trump campaign, but he made an appearance at the Republican National Convention in Cleveland, featured in the biographical video that played before Trump's address to the convention.

ABC News' Matthew Mosk and Justin Fishel contributed to this report.