Jonah Goldberg defends the wonders of fusionism:

What often gets left out in discussions of the American Right is that fusionism isn’t merely an alliance, it is an alloy. Fusionism runs through the conservative heart.

No doubt there are many movement conservatives that still endorse some version of fusionism, but it has always been and continues to be an idea designed to reconcile conflicting parts of a political movement. It is an artificial compromise position that reflected the tensions within the movement decades ago. Theoretically, it offered something to everyone in the movement and gave all factions a reason to tolerate the others while cooperating against common opponents. As a coalition-building mechanism over half a century ago, it has had its uses, but now it is mostly a fiction that movement conservatives perpetuate to maintain the appearance of continuity with the movement’s beginnings.

Of course, there are issues where libertarians and social conservatives end up on the same side for different reasons. That’s usually because they happen to oppose the same legislation or court ruling for their own reasons. It isn’t because most libertarians and social conservatives share a fusionist worldview. Fusionism doesn’t “run through the conservative heart.” The argument for the “leave us alone” coalition was that Republicans relied on different constituencies that generally favored keeping the federal government out of their affairs, and that was what held them together. Provided that the agenda was largely a negative one of opposing the expansion of government at home, these different constituencies would have a common interest in working together. Once movement conservatives started entertaining the idea of “big-government conservatism” and rallied behind the growth of the national security and warfare state, it became absurd to think that a commitment to liberty was what united conservatives in common cause.