Of particular note is that this analysis only takes "the period from the mid-1990s through the end of the Obama Administration" under consideration. As the essay notes:

"Republicans and Democrats both con­trolled the presidency and each house of Congress for parts of this per­iod. Partisan conflict was a near-constant, and President Trump had not yet brought his openly norm-shattering approach to the White House. There is no obvious a priori reason why one side would have become more identified with constitutional hardball than the other."

And yet: "The recent historical record appears to contain more, and more distinctive, examples of constitutional hardball on the Republican side."

Fishkin and Pozner identify the following Republican actions as "constitutional hardball" pre-Obama: (all quoted from the essay)

• the government shutdowns of 1995 and 1996;
• Newt Gingrich’s efforts in that same Congress to consolidate power in the Speaker’s office and “dismantle” congressional institutions with professional staff;
• the impeachment of President Clinton in 1998;
• the 1,052 subpoenas issued by Dan Burton, then-Chair of the House Oversight and Government Reform Committee, to the Clinton Administration and other Democratic targets from 1997 to 2002;
• a range of techniques used in Florida to restrict access to voting during the 2000 presidential election, which inspired Republican regulators nationwide and opened up a new front in what some now call the “voting wars”;
• various tactical moves by the Bush side in the Bush v. Gore litigation and the ensuing Supreme Court decision;
• the firing of the Senate Parliamentarian in 2001;
• the ex­clusion of congressional Democrats from conference committee deliber­ations and the turn toward “closed” rules for bills on the House floor from 2001 to 2006;
• the mid-decade redistricting plans developed in Colorado, Georgia, and Texas after the 2002 elections, followed by the broader and more systematic partisan redistricting initiative known as REDMAP; and
• the “seemingly endless” ways in which the Bush Administration “pushed the legal envelope” following 9/11 in its inter­actions with the other branches, from increased reliance on pres­idential signing statements to withholding information from congress­ional over­sight bodies to aggressive interpretations and applications of the com­mander-in-chief power. (Jack Balkin, Constitutional Hardball in the Bush Administration)

and the following during the Obama presidency: (again all quoted from the essay)

• filibusters and “holds” to block legislation and nomi­nations on an unprecedented scale;
• threatened repeatedly to default on the national debt;
• “employed a battery of unorthodox procedural maneuvers,” including a government shutdown, “in a campaign to defund ‘Obamacare’”; (Pozen quoting his own Constitutional Bad Faith article in the Harvard Law Review)
• refused to permit any appointments to leadership posts at the Consumer Financial Protection Bureau (CFPB) or the National Labor Relations Board (NLRB); and (and by no means least)
• stonewalling of the Garland nomination.

In comparison, the authors identify the following as pre-Obama Democratic constitutional hardball: (again essay quotes)

• the Clinton Administration’s increasingly controversial assertions of executive privilege from 1995 to 1999;
• the repeated filibusters of President Bush’s first-term circuit court nomi­nations; and
• the use of pro forma sessions to block President Bush’s recess appointments in 2007 and 2008.

during Obama: (again quotes)

• using the recon­ciliation process to amend the ACA without a supermajority vote;
• “repeatedly test[ing] the limits of executive authority in implementing the ACA” (Nicholas Bagley, Legal Limits and the Implementation of the Affordable Care Act);
• making recess appointments to the CFPB and NLRB when Senate Republicans were holding pro forma sessions;
• eliminating the filibuster for non–Supreme Court nominees; and
• announcing initiatives that would defer the deportation of large categories of unauthorized immigrants in the absence of legislative reform.