Gary Cameron / Reuters Like so many other prominent Republicans, Sen. Chuck Grassley didn't do much to stop birther conspiracy theories about President Barack Obama.

WASHINGTON ― Republican presidential nominee Donald Trump spent years pushing the conspiracy theory that President Barack Obama was born in Kenya, not Hawaii, and therefore could not legitimately be president.

Trump conceded this month that’s not true and it’s time to move on. But he didn’t explain why he thought it was OK to float such a flagrantly racist idea in the first place, and for so long. It probably had something to do with the Republican establishment enabling him, even if subtly.

Take Sen. Chuck Grassley (R-Iowa). In a May 2011 interview with KCJJ radio, a recording of which was obtained this week by The Huffington Post, Grassley said Trump deserved “credit” for forcing Obama to release his long-form birth certificate. This was after the show host said Trump looked “very racist” for demanding proof of Obama’s citizenship.

“Give him some credit, though, from this standpoint: He finally got the birth certificate,” Grassley said with a laugh. “Nobody else could.”

The audio clip is below. Trump comes up in the final two minutes.

(The bill never went anywhere. But notably, when the House voted later that year to commemorate the 50th anniversary of Hawaii becoming a state, some of the co-sponsors of Posey’s bill did not cast a vote.)

Grassley wasn’t part of that fringe group. But like so many other Republicans at the time, he didn’t do much to tamp down on birtherism, either. He let it percolate. A year after his KCJJ interview, he said nothing in response to a proposed plank in the 2012 Iowa GOP platform to require presidential candidates to prove they’re natural-born U.S. citizens.

A Grassley campaign spokesman did not respond to a request for comment.

GOP leaders took the same approach. They tiptoed around these racist theories about the president’s legitimacy instead of condemning them.

“This is a leadership moment here, OK?” NBC’s David Gregory said to then-House Majority Leader Eric Cantor (R-Va.) in a 2011 interview on “Meet The Press.” “There are elements of this country who question the president’s citizenship, who think that his birth certificate is inauthentic. Will you call that what it is, which is crazy talk?”

“I don’t think it’s nice to call anyone crazy,” Cantor replied.

They went back and forth, with Cantor trying to change the subject. Gregory finally asked, “Why won’t you just call it what it is? Because I feel like there are a lot of Republican leaders who don’t want to go as far as to criticize those folks who ...”

“I think the president is a citizen of the United States,” Cantor interjected. “Why is it you want me to go engage in name-calling?”

So what is the takeaway from Trump’s five-year crusade to force the nation’s first black president to prove he’s an American? It’s that a man desperate for attention was willing to appeal to the worst in people to get it, and leaders in the Republican Party were willing to go along for the ride so they didn’t lose those voters in their next elections.

That’s depressing. On a more entertaining but still depressing note, here’s some 2009 footage of lawmakers literally running away from videographer Mike Stark when asked if they think Obama was born in the United States. Republican vice presidential nominee Mike Pence, then a congressman from Indiana and chairman of the House Republican Conference, and Rep. Cathy McMorris Rodgers (Wash.), who now chairs that conference, make cameos.