It is, deservedly, Lyndon Johnson’s moment. This week, three former presidents and the current one all journeyed to Johnson’s presidential library in Austin to commemorate the 50th anniversary of his signing the 1964 Civil Rights Act into law.

Come August, we’ll have another semi-centennial moment, but it probably won’t be celebrated. Aug. 7 will mark the 50th anniversary of Congress passing the Gulf of Tonkin Resolution, which Johnson had requested to give him the authority to respond with military force to North Vietnamese attacks on U.S. ships (some of which, the U.S. government later concluded, hadn’t actually taken place). By 1965, Johnson was interpreting the resolution as carte blanche to send hundreds of thousands of American soldiers to Vietnam, 58,000 of whom died there.

Come the moment, come the man. How much credit and how much blame do we attach to this monumental figure in 20th-century history? In both his, and our, triumphs and tragedies, how do we apportion responsibility?

The landmark civil rights and Great Society legislation were the product of Johnson’s legislative genius, but of more than that as well. Just as the America that emerged from the New Deal was the handiwork of both Franklin Roosevelt and a bold, ascendant labor movement, so the more egalitarian America that emerged from the ’60s was shaped by Johnson, congressional liberals and a brave civil rights movement that aroused the nation’s conscience.

It was also the product of a political order that was nothing like today’s. Johnson wooed many Northern Republican House members and senators to back the civil rights bill. Some needed no wooing and played key roles in ensuring passage. Others got the full Johnson treatment (flattery, deals, pressure, threats — delivered at all hours in manners ranging from lofty to crude). LBJ assured Senate Minority Leader Everett Dirksen (R-Ill.), for example, that he’d go down in history for supporting the legislation.

Johnson was not the only Democrat who worked the Republicans. In the mid-’60s, a number of Republican House members and senators from the Northeast, Midwest and West came from states and districts whose workforces were 20 percent to 30 percent unionized. Many agreed with Dwight Eisenhower’s assessment a few years earlier that unions and the New Deal were realities that Republicans had to live with. They sought the support of union members at election time, and they expected the unions to lobby them when social and economic legislation was pending on the Hill.

And lobby them the unions did. About 20 years ago, I interviewed Ken Young, who had been the AFL-CIO’s chief deputy lobbyist during the ’60s (and its chief lobbyist for a number of years thereafter). In the spring of 1965, with huge Democratic majorities in both houses and with Johnson bombarding them with legislative proposals, the AFL-CIO lobbied Congress to enact 87 separate bills, Young recalled — Medicare and the Voting Rights Act most prominent among them. Eighty-five became law. The year before, it had been the federation, in conjunction with civil rights leaders, that had insisted on inserting the equal employment section, which outlawed racial discrimination in hiring, into the civil rights bill. (The original bill stopped at desegregating public facilities.) Johnson supported the expansion, and it was with that addition that the bill passed.

The credit, then, belongs to Johnson — but also to the civil rights movement and a political order in which liberal forces such as the unions held some sway with a number of Republicans and in which some Republicans were liberals themselves. Johnson would not be the Johnson we remember today without the work of Martin Luther King Jr., but so, too, is King’s legacy bound up with Johnson’s.

And if reciprocal credit is due for the landmark legislation of LBJ’s presidency, so reciprocal blame should be placed for the tragedy of Vietnam. It’s clear from the tape recordings that Johnson made of his private phone calls 50 years ago this spring that the new president viewed the prospect of going to war in Vietnam with trepidation: The conflict, he feared, would be bloody, protracted and hard to shut down. And yet, many of the key players who had been with him on civil rights — the Republicans, the AFL-CIO and his own advisers — were urging him to plunge in. Talking with his mentor, Georgia Sen. Richard Russell, in May 1964, Johnson complained about “all the senators, and Nixon and Rockefeller and Goldwater all saying, ‘Let’s move, let’s go in the North.’ ”

In the end, of course, Johnson took just enough of their counsel to wreak havoc on Vietnam, the United States, his political party and his presidency. The blame is his but, as with the credit, there’s plenty left over to go around.

Read more from Harold Meyerson’s archive or follow him on Twitter.