Former special counsel Robert S. Mueller III testifies this week before the House Judiciary and Intelligence committees about his investigation into Russian interference in the 2016 presidential election. Democrats want to shine a light on Mueller’s findings, including President Trump’s possible obstruction of justice.

The hearing will offer more than fact-finding: Committee members on both sides of the aisle will exploit the cameras to pitch partisan messages to their respective bases. It might seem that all lawmakers like to grandstand. But my research finds that there’s more method to the madness than you may realize.

Here’s what you need to know about grandstanding in congressional hearings.

How I did my research

Committees often use hearings to gather information about policy problems and potential solutions. But committee members are also prone to exploit hearings to broadcast political messages. Lawmakers take positions on policy issues, support their party or attack the opposition or grill witnesses. I call these behaviors “grandstanding.”

In my recent work, I generate a “grandstanding score” for each member of the House to capture the intensity of the political messages they deliver during committee hearings. I collected more than a million statements that committee members made in 12,820 House committee hearings between 1997 and 2016. Next, I trained hundreds of online workers via Amazon Mechanical Turk to evaluate 3,000 randomly selected statements. I randomly paired each statement with another statement, and then asked workers to determine which one of the paired statements seemed more grandstanding and less fact-based.

Based on their answers, I tagged each individual statement in the data set with a grandstanding score. The statements that included the most grandstanding received 100 points; those with the least grandstanding — and most fact-based, information-seeking — received zero points. I then tied the statement back to the lawmaker who said it and calculated each lawmaker’s average grandstanding score for each Congress. We can interpret a lawmaker’s grandstanding score as a measure of the intensity of his or her grandstanding behavior.

Lawmakers grandstand when they lack power to advance their policy agendas

Committee members who grandstand the most are those who have the least power in the committee and chamber. These members are more likely than fellow lawmakers to send political messages than delve into policy details at the hearing.

First, minority party members are about three points more likely to grandstand than their majority party colleagues. We can see this pattern in the graph below, which shows the difference in average grandstanding scores of Democrats and Republicans across the 10 Congresses studied. When the average is above the line, that means Republicans grandstanded more on average than Democrats. When the average is below the line, Democrats more frequently took political shots. Notably, Republicans grandstanded more than Democrats between 2007 and 2010, and that is the only period in which the GOP served in the minority.

There’s even more evidence that institutional status in the chamber, not personality, shapes grandstanding: Members vary in their statements over their House careers. For instance, Rep. Brad Sherman (D-Calif.) grandstanded more in hearings when he was a minority member in 1999-2000 (scoring 54.78) than when Democrats took back control of the House after 2010 (scoring 47.66).

Second, minority party members are especially more likely to grandstand by a greater margin when the majority party also controls the White House. That makes sense, because that’s when minority party members are especially disadvantaged in moving their bills forward.

However, both parties grandstand more during periods of divided control. It might seem odd that minority party members grandstand more when their party controls the White House. Most likely, under divided government, opposition party chairs will more often hold hearings on partisan issues to hold the opposition administration accountable, which increases minority members’ incentives to grandstand to counteract the majority party’s messaging.

Some committees invite more grandstanding than others

If lawmakers are more prone to grandstand when they can’t legislate, grandstanding should be more prevalent in committees that limit the influence of rank-and-file members. That means we should see more grandstanding in the more powerful committees (say, Rules, Budget, and Ways and Means) and those covering foreign policy or security issues typically dominated by the president (such as Foreign Affairs and, recently, the Select Committee on Benghazi).

The graph below shows the average grandstanding score by committee. Note also that grandstanding is far less frequent in committees known for their constituency focus (such as Agriculture, Natural Resources and Veterans Affairs), where lawmakers have greater opportunity to push for their districts’ interests.

Ideologues are not necessarily grandstanders

Interestingly, ideologues are not more prone to grandstanding. Below, I show grandstanding scores for all House members in 2015-2016, mapped against each member’s ideological score (as measured by DW-NOMINATE). The higher this ideological score, the more conservative. I indicate the names of the most and least grandstanding members. (Those who made fewer than 10 statements appear in gray.)

None of the most intense grandstanders hails from the outer wing of their party. If anything, these grandstanders are more likely to be party centrists, a pattern I find throughout the period studied.

When Mueller appears before the House Intelligence and Judiciary panels, expect to hear more politics than facts. But don’t expect equal grandstanding from every lawmaker. My research suggests you can expect more grandstanding in Judiciary than in Intelligence. And Republicans should be especially likely to seek the limelight by appealing to partisans back home, attacking the Democrats and protecting the president.

Ju Yeon Park is a postdoctoral research fellow at the School of Computing and Information at the University of Pittsburgh.