McCaskill isn't popular, but the GOP's claim that she's the worst doesn't check out

"Congrats to @clairecmc for being named most likely to be the most unpopular senator in the United States for four months in a row! Quite an accomplishment! #MOSen," the party tweeted Sept. 10 as part of its support for challenger Josh Hawley.

Being named as the least popular senator in the country would be an unwanted title, so we wanted to check into the Missouri GOP’s claim.

We reached out to the Missouri Republican Party multiple times by email and received no reply. But small text in the tweet’s photo credited the claim to a Morning Consult poll.

Morning Consult is a technology company that works in collecting and understanding data. It has a newsroom section that focuses on data reporting, like data from senator approval rating polls.

The Morning Consult poll in question shows the 10 top-ranked and bottom-ranked senators in the country. Each senator’s percentage rankings have a different margin of error, ranging from 1 to 6 percentage points. The margin of error for McCaskill’s is 1 percentage point.

Morning Consult’s methodology has various aspects to it. Surveys are sent out online to registered voters in each state. The questions asked of each respondent only included subjects about their voting preferences and specifics about their state’s senator.

For Missouri, each poll received between 7,000 and 9,000 responses from registered voters. Party affiliation of the voters is not broken down by state.

The poll is conducted quarterly, not every month, as readers of the GOP tweet might think. And it doesn’t rank which senator is the "most likely to be the most unpopular senator." The polls contain approval, disapproval and unknown/undecided ratings.

McCaskill was the fourth-least popular senator in the nation in the July 25 poll. Sen. Mitch McConnell, R-Ky., was the least popular.

In Morning Consult’s April and July quarterly polls McCaskill had a 44 percent disapproval rating.

Her approval rating dropped by 1 percentage point to 39 percent from April to July.

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Morning Consult more frequently updates the poll for the 10 incumbents in highly competitive races. The September update, released before the tweet, showed McCaskill had a 46 percent disapproval rating, the highest among the other selected senators on the ballot in 2018.

The poll also has a question in which voters are asked if they think it is time for someone new. McCaskill received the second-highest ranking of respondents saying yes, at 53 percent. That was behind Florida Sen. Bill Nelson, another Democrat, at 54 percent.

The tweet is more than a month old, so we wanted to look at the most recent ratings.

As of the most recent update Oct. 3, McCaskill was up to a 48 percent disapproval rating. McCaskill’s disapproval rating has been increasing since the 44 percent in July, but has never eclipsed McConnell to be the senator with the worst disapproval rating.

McCaskill’s time for a new person rating has also gone up to 54 percent from the October update, but it is still behind Nelson’s by one percentage point.

Morning Consult has also released its third-quarter senator rankings, and McCaskill is now the third-least popular. Although they do show that McCaskill has climbed up one rank, she is still not the most unpopular senator.

Polling experts we talked to noted that registered voters are more likely to be Republican, which could lead Democrats on Morning Consult polls to have inflated disapproval statistics.

Cliff Zukin, Rutgers University professor of political science and public policy, brought up that the results from the surveys are brought from volunteer responses, which is not as accurate as a true scientific sampling method. Because the respondents would volunteer to answer the survey, it is not as representative of the underlying population as a completely random sampling method would be.

Claiming that disapproval rating and being the "worst" are not as linked as one might think. Kenneth D. Wald, University of Florida professor emeritus of political science, claimed that politicians making decisions on polarizing topics will usually increase their disapproval rating as they would upset a some group of people.

The Missouri GOP said, "Congrats to @clairecmc for being named most likely to be the most unpopular senator in the United States for four months in a row!"

The tweet is sloppily worded as there is no such designation for being named "most likely to be the most unpopular senator."

McCaskill’s popularity is low among her peers up for re-election. But she isn’t the most unpopular. McConnell held that position in July and has kept it through to October.

When compared to certain vulnerable incumbents, she does have the highest disapproval rating in the country. The Missouri GOP tweet said that she is the most unpopular senator in the country, which does not reference solely incumbents running for re-election.

We rate the statement Mostly False.