I know that Yuan Shikai attempted to revive the Chinese monarchy in 1915. How popular was this idea at the time, and to what extent did it persist under the nationalist and communist regimes?
An important question to ask about residual monarchism under the early Republic is whether a distinction was seen between the establishment of a new monarchy a la Yuan Shikai in 1915, and the restoration of the Manchu monarchy as was briefly attempted in 1917. The reason I bring this up is because Yuan was not attempting to 'revive the Chinese monarchy', not least because the Qing were not Chinese and had a distinct style of ruling, but instead was trying to establish his own system, a centralised, nominally constitutional monarchy modelled after Japan or Germany.
It's more than clear that a restoration of the Manchu Qing was very much off the table, even in the chaos following Yuan's death. Politics had moved on in the wake of the revolution, and while a few old moderate constitutionalists like Kang Youwei supported Puyi's restoration in 1917, the constitutionalist faction as a whole had since 1898 already moved in a more radical direction under the overall leadership of Liang Qichao. Under Liang's leadership, the Republican Party of Li Yuanhong, the the Unity party of Jiang Binglin and the Democratic Party of Tan Hualong merged into the pro-republican Jinbudang (JBD for convenience), or Progressive Party, in 1913 – ironically this was arguably the more politically moderate of the two major political parties, when compared to Sun Yat-Sen's Kuomintang (KMT), or Nationalist Party. The pro-Manchu Royalist Party was effectively unrepresented in the official channels of power, and its activities were primarily confined to anti-Republic sedition in Manchuria and Inner Mongolia – indeed in the event Zhang Xun's attempt at a restoration in 1917 was barely linked at all to the official Royalist movement, though it proved destabilising enough to lead to Li Yuanhong's resignation as President shortly following its suppression. It must also be noted that Manchu rule was a specific grievance of many anti-Qing elements, radical constitutionalists and revolutionary republicans alike, and so the reestablishment of foreign Manchu rule would have been markedly more unpalatable than a Han Chinese monarchy.
However, Yuan may not have been totally delusional when he made his own bid at the throne. For one, the suppression of the Nationalist Party in November 1913 meant that, ostensibly, the most powerful ideological opposition to a new monarchy was gone. Voter turnout to the Assembly elections earlier that year had been quite low, and in any case the franchise was property-based, so although the the KMT gained a sizeable plurality in both houses of the National Congress, with 48% of the Senate and 45% of the House under their control, the Nationalists probably came to power off the back of a very vocal radical minority, with Yuan still in reasonable standing with the broadly moderate consensus. Although the JBD was a relatively distant second in the Assembly, holding only 22% and 26% of the seats in the higher and lower houses, respectively, that still left a substantial number of minor parties and independents who, in all, seem to have been moderates leaning either pro-Yuan or relatively neutral. Although Yuan dissolved the Assembly outright in January 1914, he took 66 of the remaining members to form a nominal rump Assembly, which although not very warmly received by the JBD, nonetheless seems to have been a relatively stable arrangement, which Yuan (at least in public) acknowledged as a temporary measure against radical derailment of the revolution.
For another, Yuan's decision to declare a new monarchy must be seen in the context of a fundamental problem besetting the post-revolutionary order, namely that while the initial goals of the revolution itself, those being the overthrow of the Qing and establishment of a republican government, were shared by most major parties involved, there was very little agreement on how the republican state should be structured. In the last years of the Qing, the republican faction supported the idea of a strong state with popular mandate, whereas the radical constitutionalists had envisioned the continuation of the process of decentralisation begun with the emergency measures against the Taiping in the 1850s, with an end goal of establishing powerful regional governments representing elite interests answering to a central government similarly dominated by regional representatives of the property-owning elite. While Yuan had been no republican, he did not share the decentralising tendencies of the radical constitutionalists, either, but instead had generally been aligned with the more moderate constitutionalists of Kang Youwei, who had advocated a system in which imperial power was more circumscribed, but where power was nonetheless still invested in a central government balancing imperial and regional interests. Shan argues that Yuan, despite his distaste for the republicans, nonetheless was a centraliser, and that as such, he had always seen the presidency as a relatively autocratic role. In turn, the emperorship may well have appeared like a logical step forward in securing a restrengthened central government and arresting the particularising tendencies of the Late Qing.
There's also the particular circumstances of the imperial appointment to consider. Yuan had in August 1915 begun investigating the possibility of establishing a monarchy, probably under the assumption that the JBD and similar would not particularly object to the replacement of the presidency with a monarchy given their former status as constitutionalists. And, in the event, the rump Assembly did approve and petition for Yuan's accession in December 1915. Obviously, said assembly was headed by Yuan's cronies, although he may not have been too far off regarding moderate interest in a new monarchy. The warlords of the provinces which first rebelled in the National Protection War following Yuan's attempted accession – Yunnan and Guizhou – were predominantly Japanese-educated former members of Sun Yat-Sen's Tongmenghui, and generally not radical constitutionalists, although there were of course exceptions. We must also consider that Yuan's information flow was increasingly being handled by a small clique of men, including his son, who allegedly bribed newspaper publishers in Beijing to produce special, erroneous copies for Yuan specifically, which may further have helped distort his view of the public's reception of a new imperial accession.
In sum, then, Yuan's decision to establish a monarchy in 1915 was not entirely without good cause. Following the suppression of the KMT, the main political party was the successor to the late Qing constitutional monarchist faction, making the prospect of a monarchy a reasonably realistic one from a pragmatic standpoint; Yuan's own (mis)interpretation of the role of the presidency and general inclination towards centralisation made an imperial reestablishment appear like a relatively small step in the right direction; and Yuan's immediate supporters seem to have done much themselves to push Yuan towards the imperial title. In the event, we may never know for sure how far there was broad support for Yuan's monarchy given both its extreme brevity and the general dominance of regional and capital elite strongmen in political affairs. However, it must be said that there was at least the perception that certain people in the political class might not be disinclined to a new Han Chinese monarchy. What is probably certain is that there were very few enthusiastic about creating it. The republican revolution had done little to enfranchise the general public, whose political interests thus would have lain outside the official republican organs of power, and those military and plutocratic elites who had gained power thanks to the revolution, particularly in the wealthier south of China, were evidently not inclined to giving up their newfound authority, given the rapidity with which the anti-Yuan faction in the National Protection War spread.
Sources, Notes and References
Patrick Fuliang Shan, Yuan Shikai: A Reappraisal (2018)
Ernest P. Young, 'Politics in the Aftermath of Revolution: The Era of Yuan Shih-k'ai, 1912-16' in ed. John K. Fairbank, The Cambridge History of China, Volume 12: Republican China, 1912–1949, Part 1 (1983)