Having offered the North a free California and abolition of the slave trade in the District of Columbia, Clay hoped it would come on board for the proposals designed to appease the South. To offset a free California breaking the even sectional balance of the Senate, Clay proposed a mix of fairly naked bribery and hope to the South.
The Texas Republic ran up large debts in its decade as a semi-independent nation. Those debts remained a great burden on its government, as the United States did not assume them. Worse still, Texas planned to pay them off via tariffs that as a state it could no longer levy. So the Clay Measures offered to assume Texas’s debt in exchange for Texas surrendering its claims to vast swaths of territory it never controlled.
This resolved the border dispute with New Mexico and paved the way for organizing that territory under two territorial governments: the eponymous New Mexico Territory and Utah. These territories did not correspond to modern state boundaries. New Mexico included the modern state and all of modern Arizona, the southern corner of Nevada, and a piece of southern Colorado. The Utah territory contained that modern state, the remainder of Nevada, about a third of Colorado, and a section of Wyoming.
That amounts to a lot of land, but the normal course of development entailed territories shrinking as the population grew and portions came in at states at different times, with the rump remaining a territory. The Northwest Territory became Ohio and the rest became Indiana Territory. Arkansas Territory split between that state and Indian Territory, to which Jackson exiled the Five Civilized Tribes of the old Southwest along the Trail of Tears. Everyone understood that those two territories probably meant more than two states. That kind of size complicated both Texas Annexation and California’s statehood bid, as both came in much larger than the states out East. Established practice would have divided them. Polk’s Missouri Compromise extension plan would have likewise bisected California. Clay offered a return to past practice and the hope of as many as four new slave states with their eight slave state Senators and four (to start) slave state Representatives over the next few years.
Clay’s plan left no territory in the Mexican Cession unorganized. No new Californias would blindside the nation. No blank territorial slates remained for slavery to expand to or be barred from, as the other unorganized territory in 1850 rested within the Louisiana Purchase and thus fell under one of Clay’s old Missouri Compromise. (Aside the modern Oklahoma Panhandle, which the compromise accidentally made unorganized.) It resolved the lingering Texas border issue and offered Texas plenty of cash to accept that settlement.
Between what Clay offered the North and his territorial settlement for the South, with its potential for future slave states, the crisis might appear defused. But the South had another great complaint against the North, even in the days when the Wilmot Proviso failed to become law and the Free Soilers took only 10% of the vote. As that last concern would sweep most of the rising sectional tension leading up to the war under its banner, the problem of what to do about runaway slaves deserves its own post.