President-elect Donald Trump announced Friday that he will nominate Sen. Jeff Sessions (R-Ala.) to run the Justice Department. A few years ago, this would have a startling pick.

Sessions has always been one of the most conservative senators in the GOP, a fringe figure perhaps best known for his hard-line views on immigration. Now, if confirmed as attorney general, he will become the nation’s top law-enforcement officer.

The mainstreaming of Sessions reflects just how much politics has changed of late. His rise to prominence has as much to do with Trump as it does with his party’s recent swerves to the right.

When he was first elected to the Senate in 1997, Sessions was one of the nation’s five most hard-line Republican senators, along with James M. Inhofe (R-Okla.) and Jesse Helms (R-N.C.). But ever since the tea party shook up Congress in 2010, Sessions has found himself moving closer to the center of the GOP.

His own views haven’t softened. Rather, his colleagues are getting more extreme.

This chart shows the evolution of the Republican and Democratic members of the Senate over the past century using a common measure of political polarization. Both parties have been pulling away from each other in recent decades. But during the past five years, the Republican Party took a particularly sharp right turn.

This scoring system, which was developed by a group of political scientists, assigns each lawmaker a number depending on how polarized their voting habits are. The red zone on the chart shows the range of scores for Republican senators over time, while the blue zone on the chart shows the range of scores for Democratic senators. Higher scores indicate more conservative voting patterns, while lower scores indicate more liberal voting patterns.

Republicans who lie above the red zone — like Sessions in his early career — are more conservative than 90 percent of their fellow party members. Likewise, Democrats who lie below the blue zone are more liberal than 90 percent of other Democrats. In the 1940s, there was considerable overlap between Democrats and Republicans, but since the 1980s, they have grown further and further apart.

Today, Sessions is still more conservative than about three-quarters of his GOP colleagues, but he’s no longer an outlier. He’s been flanked by people like Sens. Mike Lee (R-Utah) and Ted Cruz (R-Texas).  

During his time in the Senate, Sessions made a name for himself as an advocate for tougher immigration laws. He has repeatedly lobbied for increased security on the Mexican border, wants to reduce legal immigration, and claims that there is “a clear nexus between immigration and terrorism.”

Attorney General Jeff Sessions has been implementing big changes at the Justice Department. (Thomas Johnson/The Washington Post)

On one hand, this nomination makes a lot of sense for Trump. Sessions was the first sitting senator to endorse Trump, and his border-hawk views align well with the Trump brand. He has been a close adviser to the campaign, a loyal surrogate and serves as vice chairman of Trump’s transition team. It was widely expected that Sessions would be rewarded with some kind of appointment.

On the other hand, Sessions carries a lot of racial baggage. As my colleagues have pointed out, Sessions was once denied a federal judgeship over allegations of racist behavior, and he has gone on record opposing the Voting Rights Act. Yet, if he is confirmed, Sessions will be the nation’s chief officer in charge of protecting civil rights and voting rights. That would be, well, interesting.