President Obama said Thursday that the Republican Party is responsible for Donald Trump's rise, for "over a course of time, creating an environment where somebody like Donald Trump can thrive." Obama refuted the argument that Trump's surge is a reaction to his presidency.

"He's just doing more of what has been done for the last 7 1/2 years. And, in fact, in terms of his positions on a whole range of issues, they're not very different from any of the other candidates," Obama said in response to a question during a news conference with Canadian Prime Minister Justin Trudeau.

Obama said he had heard the argument from critics that the increasingly polarized political environment under his presidency contributed to Trump's candidacy, and the heightened rhetoric this campaign.

"I have been blamed by Republicans for a lot of things, but being blamed for their primaries and who they're selecting for their party, is novel," Obama said with a laugh.

Obama did admit, as he had in his State of the Union address earlier this year, that he regrets the nasty tone politics has taken under his presidency.

"I do all kinds of soul searching in terms of are there things I can do better to make sure we're unifying the country? ... I am more than happy to own the responsibility as president ... to continue to make efforts to bridge divides and help us to have common ground," he said. But he stopped short in connecting that to Trump's candidacy, saying he has not contributed to "that tone of politics."

"What I'm not going to do is validate some notion that the Republican crackup that's taken place is a consequence of actions that I've taken," he said.

Instead, he said the "Republican political elites and many of the information outlets" are to blame for perpetuating the notion that "there is a 'them' out there and an 'us' — and the 'them' are the folks who are causing whatever problems you're experiencing."

Obama also called on "thoughtful conservatives" who are "troubled by the direction of their party" to "reflect on what it is about the politics they've engaged in that allows the circus we've been seeing to transpire."

"I want an effective Republican Party," Obama said. "I think this country has to have responsible parties that can govern and that are prepared to lead and govern ... whether they occupy the White House or not."

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