(CNN) Judge Brett Kavanaugh is one of the least popular Supreme Court nominees of all time. But as long as his popularity ratings don't drop dramatically, he's likely to get confirmed.

Usually, Supreme Court nominees are well liked even after intense confirmation hearings. Just after Kavanaugh was announced, I collected the final popularity ratings for all Supreme Court nominees since Robert Bork before their confirmation vote or withdrawal. (No poll was taken about Anthony Kennedy.)

The average net approval or favorability rating for these nominees was 20 percentage points.

Kavanaugh's net favorabilty rating is just above zero right now. No nominee who was as unpopular as Kavanaugh is currently has been confirmed in the modern era. Harriet Miers withdrew her nomination after being chosen by President George W. Bush, while Bork was voted down after being nominated by President Ronald Reagan.

Kavanaugh's low popularity certainly limits his potential to grab Democratic votes. Once we control for factors such as a nominee's qualifications and her or his ideological distance from each senator, a nominee's popularity has impacted how many votes they receive for confirmation. One of President George H.W. Bush's picks, Clarence Thomas, for example, probably wouldn't have been confirmed without his strong popularity ratings.

The problem for those hoping that Kavanaugh goes down is that popularity isn't the only thing that matters. Miers withdrew mostly because conservatives complained about her qualifications . Bork was voted down by a Democrat-controlled Senate because his conservative record was so extensive.

Kavanaugh has neither of those problems. He has been rated as "well-qualified" by the American Bar Association. Kavanaugh also will be voted upon by a Senate that is controlled by Republicans.

When you combine the makeup of the Senate and Kavanaugh's judicial profile, his current popularity rating is probably not low enough to make any Republicans vote against him. He may even pick up a Democratic vote.

Now, the potentially good news for Democrats is that nominees do tend to see their popularity drop after a confirmation hearing.

Bork, for example, initially had a one-point net favorability rating in a Times Mirror poll. That's more than 10 points higher than where his popularity rating ended up in a Los Angeles Times poll before the Senate voted him down.

When I previously wrote on Kavanaugh, I noted that a Bork-like popularity might be low enough for Kavanaugh to get voted down. Specifically, it would on average lead to him getting 49 votes in favor compared to 50 votes against.

That, however, was back when Sen. John McCain was not healthy enough to be in Washington to vote on Kavanaugh's confirmation. In other words, back when Republicans really had only 50 senators to the Democrats' 49.

This week, Republican Jon Kyl was sworn in to fill McCain's seat. Kyl has a conservative voting record and was Kavanaugh's sherpa (i.e. the experienced Washington insider to guide him through the confirmation process ). There is pretty much no chance that Kyl would vote against Kavanaugh. That brings Kavanaugh to 50 votes on average in a hypothetical scenario in which his popularity matches the worst polling nominee on record by the end of the confirmation process.

I guess it's possible that Kavanaugh could become even more unpopular than Bork was. In this highly partisan environment in which potential justices are far less likely to reveal their stances on matters of judicial importance than they were back when Bork was under consideration, it seems unlikely, however, that Kavanaugh's public numbers would move that much.

It's also possible that Kyl's connection to Kavanaugh might make him abstain from voting on him. Again though, that seems more like a Democratic fantasy than a potential reality.

The bottom line is that with 51 Republican senators, he's very likely to land on the Supreme Court.