Sen. Pat Roberts (R-Kan.) is one of seven current senators who voted on the nomination of Merrick Garland to the D.C. Circuit Court in 1997. Roberts, like the other six still-serving senators, voted to approve Garland, who President Obama nominated Tuesday to the Supreme Court.

This time, though, Roberts doesn't seem to be interested in voting for Garland. Asked by CNN's Manu Raju if he would support Garland once again, Roberts replied that "it's not about the person" -- suggesting that he'd stand with the Republican majority in refusing to move Garland's nomination.

Arguments that Garland should be confirmable by the current Senate because he was confirmed by the Senate in 1997 often overlook a critical point: The Senate has gotten much more conservative over the past 20 years.

VoteView, a site run by political scientist Keith Poole, tracks the partisanship of members of Congress over time on a simple -1 to +1 scale. It allows us to track the partisanship of elected officials -- and party caucuses -- between the 105th Congress that approved Garland and the 113th, the most recent Congress for which data is available.

In 1997, the Democratic caucus in the Senate scored an average of -0.35 on the VoteView scale, and the Republicans scored a 0.39. By the 113th Congress, excluding members who are no longer serving, the Democrats had shifted slightly left to -0.39. The Republicans had moved hard to the right, with an average of 0.57.

What's more, five of the seven Republicans who voted to approve Garland in 1997 moved to the right as well. Sen. Susan Collins (Maine), one of the most moderate members of the Senate, moved to the middle. Sen. Jim Inhofe (Okla.), one of the most conservative, moved to the right. Worth noting: None of the seven moved as far to the right as Roberts.

In January, we looked at how partisan Congress has grown over time. Republicans have gotten much more partisan than Democrats, as is made clear even just looking at the change since 1997.

The two nominations of Merrick Garland are happening at two very different political moments -- the election year notwithstanding. Pat Roberts is living proof.