Last week, 126 House Republicans signed onto a brief supporting Texas’s lawsuit asking the Supreme Court to overturn the results of the 2020 presidential election. The court summarily rejected Texas’s bid, leading one Republican senator to declare that the justices had “closed the book on the president’s [legal] nonsense.”

Lawmakers occasionally sign onto these “friend of the court” efforts, especially because legislators can file such briefs without any formal action by the House. Still, this brief stood out. Monday night in a national address, President-elect Joe Biden joined observers on both sides of the aisle in decrying the underlying legal push as deeply anti-democratic. GOP lawmakers who signed on from the states targeted by the suit — Michigan, Georgia, Pennsylvania and Arizona — in effect were calling on the court to throw out thousands of votes of their own constituents.

So why did over half of the House Republican conference sign on? As did political scientist Matt Green in similar analysis, I’ll explore the potential impact of a broad range of political, personal, and partisan forces that might have shaped lawmakers’ decisions on whether to sign on.

Here’s what the data tell us.

Lawyer-lawmakers split

Let’s dispel the notion that lawmakers who sign briefs on cases before the Supreme Court know more than their colleagues about the legal issues at stake. If that were true, legislators with law degrees would be more likely than their colleagues to sign onto amicus briefs. But research finds precisely the opposite: House members with law degrees disproportionately do not sign these briefs.

In this case, Republican lawmakers with Juris Doctors were no more or less likely than their colleagues to endorse the Texas lawsuit. Just over half of the 58 Republicans who hold law degrees signed on. Given a conservative Supreme Court’s unanimous rejection of Texas’s effort to interfere in other states’ elections, it’s hardly surprising that legal chops don’t correlate with signing the brief.

Ideology trumps all

In contrast, a clear pattern emerges when we examine the signers’ ideological orientations. Using lawmakers’ floor voting records, the more conservative the Republican, the more likely it is that he signed the brief. Or that she did — as eight of just over a dozen GOP women joined Republican men in signing.

Why would more conservative lawmakers be more likely to defend Trump? We typically use lawmakers’ votes as a proxy for their ideological orientations. But legislators’ votes grow not just from personal ideology but are also shaped by a broad array of forces — including constituent pressures and partisan loyalty. As it turns out, the most conservative House Republicans are also the most pro-Trump — including Reps. Jim Jordan of Ohio, Steve Scalise of Louisiana, and Dan Bishop of North Carolina. Most likely, conservative stalwarts jumped on the brief to demonstrate their continued loyalty to Trump.

Hedging electoral bets?

It’s possible that conservative gusto for Trump’s refusal to concede the election just reflects a simple electoral bet. Republicans looking over their shoulders at Trump’s loyal partisan base back home in their districts — constituents who overwhelmingly tell pollsters that they believe Trump’s false claims that the election was stolen — have little electoral incentive to abandon Trump’s claims. So long as Trump remains popular back home and continues to dangle the possibility that he might run again in 2024, Republicans from the reddest districts should be eager to sign the brief while those in swing districts might hesitate.

Although signers disproportionately hailed from redder districts, that relationship peters out when we take account of lawmakers’ ideological orientations and electoral ambitions. With Trump still so popular among GOP voters, even swing-district House Republicans may wish to head off being “primaried,” no matter how many state and federal courts have rejected Trump’s claims.

Easy call for those calling it quits

One group of House Republicans found it easy to resist signing the brief: those retiring at the end of this Congress. By my count, two-thirds of the 21 GOP members retiring this year (excluding those defeated at the ballot box or leaving to run for higher office) refused to sign the brief. Severing the electoral connection likely freed lawmakers to act as they pleased, even knowing Trump was watching who signed.

Notably, the most conservative of the retiring Republicans still signed onto the brief. Perhaps those retiring conservatives still see elective office in their futures; perhaps they’re just all-in Trumpists. Either way, severing the electoral cord still has its limits in a Trumpian era.