Last month, a majority of the U.S. House of Representatives voted to grant statehood to Washington, D.C. The bill appears to be dead-on-arrival in the GOP-led Senate, as Republicans expect that D.C. voters would elect two Democrats to fill the state’s two new Senate seats.

Senators are sparring about more than partisanship. Consider how Sen. Tom Cotton (R-Ark.) contrasted Wyoming and the District, which has about 150,000 more people than Wyoming. Cotton argued that the state, despite its small population, is unlike D.C. in that it is a “well-rounded working-class state.”

Cotton also called out the District’s current leadership for being too lenient toward the recent protests and asked whether Americans could trust Mayor Muriel E. Bowser — or the city’s controversial former mayor, Marion Barry — to run a state. Democrats and media outlets labeled Cotton’s reference a racial dog whistle because it suggested that the African American mayors of a city with an almost majority-black population — and the nation’s capital — were unqualified to govern.

The last time Congress and the president admitted new states was 60 years ago, when Alaska and Hawaii achieved statehood. Cotton’s comments echo the long history of debates in this country about the criteria for admitting new states to the union. Here’s what you need to know about these public discussions.

Partisanship was always an issue

In the decades before the Civil War, Congress attempted to “balance” the regional conflict between north and south over the expansion of slavery by admitting two states at a time. That way, neither side would gain further political advantage.

After the Civil War, balancing declined. Republicans dominated the federal government for decades. Eyeing what they believed would be new Republican-leaning states out West, around 1890 Republicans moved to entrench their majority in Congress, successfully pushing to admit a slew of states (North and South Dakota, Montana, Idaho, Wyoming and Washington).

Granted, Republicans failed to predict the partisan preferences of these states perfectly — they lost all but North Dakota to the Democrats in 1896. But Republicans were pretty good prognosticators: In the 2000s, only the state of Washington has supported a Democratic presidential candidate.

Racial currents permeated these debates

Statehood debates have long centered on questions of whether the population of the territory was perceived to be capable of self-governance. Such debates frequently revolved around race.

In my recent book, “Building an American Empire,” I examined statehood debates to understand the politics of American expansion. I paid particular attention to the failed efforts to admit new states. Some of these, such as New Mexico and Hawaii, eventually passed at a later date. Others never came to fruition, such as the Grant administration’s 1870 effort to create a future state in Santo Domingo (now the Dominican Republic).

At the time, many members of Congress argued that only territories with majority-white populations deserved statehood. Because most territories under consideration were made up overwhelmingly of white voters, race was not discussed in every instance. But every time the territory under consideration had large numbers of people Congress considered to be nonwhite, debates were controversial, and statehood frequently failed. Often these statehood efforts stalled until Congress became convinced that a majority of the territory’s voting population was white.

Consider New Mexico. It joined the United States as a territory in 1848 and remained so until becoming the final of the contiguous 48 states incorporated (with Arizona) in 1912. In one of the earliest votes over statehood, in 1876, Sen. Lot Morrill (R-Maine) opposed the territory because it was predominantly populated by “Indians, the men that we hunt when we have nothing else to do in the summer season” and “Mexicans, Spaniards, and greasers.”

New Mexican statehood stalled into the 1900s, as Sen. Albert Beveridge (R-Ind.), the head of the Senate Committee on Territories, consistently opposed statehood because the territory lacked a white majority. In 1906, he attempted to combine New Mexico with Arizona to incorporate a large white population into one future state. The overwhelmingly white Arizonans protested that they did not want to be included with a people “of different traditions, customs and aspirations.”

By 1912, Congress was finally satisfied that the population of New Mexico had increased in a “good” way. As one advocate of statehood put it: “Americans are coming in there by the thousands every year. The entire increase of population … is what we would call Americans. There is no increase by immigration among the Mexicans.”

Lawmakers often did not take seriously statehood for other territories because too few white people lived there. For instance, Indian Territory, established in 1834, received scant support for statehood despite its official status as a territory (a designation that typically suggested a path to eventual statehood).

Discussions heated up in the 1880s, when many hundreds of thousands of white settlers populated Indian Territory — which by then had been whittled to the current borders of Oklahoma — via federally sponsored land runs. Congress subsequently voted to incorporate the now overwhelmingly white Oklahoma as a state. At the same time, Congress ignored an effort by voters in the still racially diverse part of the territory to establish a second state, Sequoia.

What are the parallels to today’s debate?

The District fits into this long historical pattern, as do recurring debates over Puerto Rican statehood and last century’s lengthy conversations about Hawaii. In the aftermath of George Floyd’s killing, Americans are having an exceptional collective moment of self-reflection and historical recognition of the nation’s often exclusionary and racist past. Protesters and politicians alike are taking down statues and removing famous historical figures from buildings and communities.

As Cotton’s comments suggest, the debate over D.C. statehood is a part of this conversation. African Americans have represented a majority or near-majority of the District’s population since the 1950s, and more than a third of the population since the Civil War.

Questions regarding the District’s fuller inclusion into the American polity importantly engender questions about the meaning of citizenship and representation, as well as the restraints the nation has historically imposed on people of color.

Paul Frymer is professor of politics at Princeton University and author of “Building an American Empire: The Era of Territorial and Political Expansion (Princeton University Press, 2017).