Almost a year into Donald Trump’s presidency, the border wall he passionately promoted throughout his election campaign amounts to eight prototypes, no more than 30 feet long each, sitting in a desert outside San Diego.

No funding has been appropriated by Congress to advance the project beyond the testing phase. There’s no final design. And despite Trump’s rallying cry that Mexico would pay for the barrier, that country hasn’t contributed a peso.

The wall, an emotional centerpiece of Trump’s populist candidacy, is resurfacing as Washington turns from tax legislation to a fight over government spending for the rest of the fiscal year. A spending package Congress plans to debate in January will test whether his promise can ever be fulfilled.

Tensions over immigration are returning to center stage as Democrats seek to use the January spending measure to restore legal protections against deportation to hundreds of thousands of people brought to the U.S. illegally as children. Trump has said he would like an agreement to fund the wall in return, and he resumed pressing for the wall even as he celebrated Republicans’ tax overhaul.