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Want a less partisan senator? Elect a former governor.

Former GOP presidential nominee and current GOP candidate for Senate Mitt Romney addresses supporters while his family looks on at their campaign headquarters during a primary election night party on June 26 in Orem, Utah. (Rick Bowmer/AP)

Voters in six states this year will have a chance to put a former governor in the Senate. Republican Mitt Romney of Utah, Democrat Phil Bredesen of Tennessee and Republican Rick Scott of Florida are trying to get elected to the Senate, while Joe Manchin III (D-W.Va.), Tim Kaine (D-Va.) and Angus King (I-Maine) are running to hold their seats.

On the campaign trail, several of these candidates have told voters that they won’t be afraid to stand up to their party when they disagree. Romney has said he will “take a different course” from others in the Republican Party and will “speak out” when he disagrees with President Trump. Bredesen has pledged not to be a “toy of the national Democratic Party.” Scott has promised he “won’t fit in Washington.”

Candidates make noises like this all the time in an effort to show how principled they are. But our recent research suggests there may actually be something to these pronouncements. When former governors join the Senate, they tend to be less partisan in their voting behavior than their colleagues who have never been a state chief executive.

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Former governors are less loyal to their parties

We draw that conclusion from an analysis of legislators who served in the Senate between 1983 and 2015. We use Party Unity scores, which indicate the percentage of votes a legislator casts with his or her party during “party votes” — situations where a majority from each party opposes the other.

We found senators who had served as a state governor had, on average, a party loyalty score 8 percent lower than other members. This is not to say former governors regularly go rogue; like most Republican and Democratic legislators, they usually vote with their parties. But they were measurably more independent than their fellow senators, even when we account for a variety of factors that influence party loyalty.

We also found that the length of a governor’s time in office mattered. For each year that a senator had served as a former governor, there was a 1 percent reduction in party loyalty score. Notably, we don’t find that other types of previous political experience — for instance, serving as a state legislator — differentiate senators the way that being a former governor does.

Our findings are certainly consistent with the reputations and records of the current crop of former-governors-turned-senators. While the median Democratic Party loyalty score from 2013 to 2015 was 98.5 percent, the scores for Kaine (97) and Manchin (81) were lower. King, an independent who caucuses with the Democrats, voted with the Democrats 43 percent of the time.

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Why are governors less partisan?

In our research, we offer two primary explanations for our findings. First are the experiences that governors have in office. Because most state executives are given broad discretion over budgeting and bureaucratic management, many former governors transitioning to Washington are used to exercising unilateral power and have little patience for the partisan gamesmanship they experience once in the Senate. Because governors must often broker compromise between parties in the state legislature to enact policy, those who make the transition to the Senate tend to be comfortable working across the aisle.

For example, in response to their collective frustration with the Senate’s slow pace of business, a bipartisan group of former governors serving in the Senate decided to form a “Former Governors Caucus,” which Sen. Thomas R. Carper (the former governor of Delaware) joked was like a “support group” for “[m]en and women who used to be somebody and be special.”

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Second, governors (or at least those governors popular enough to mount a successful Senate run) possess some strategic advantages that may give them more freedom to buck their own party. Like senators, governors must build statewide electoral coalitions to win office. But unlike most senators, they enter the Senate with well-established reputations with voters and are less reliant upon the national parties for financial support.

In our analysis, we used the Database on Ideology, Money in Politics, and Elections to compare former governors’ donor networks to those of other senators. Former governors’ supporters are less ideologically extreme than their colleagues’ — even those of former House members from small states who, like governors, represented their entire states. This more moderate fundraising base may insulate former governors from the disciplinary tactics of party leadership.

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The recent dust-up between Manchin and Senate Minority Leader Charles E. Schumer (D-N.Y.) over President Trump’s Supreme Court nominee may help illustrate the point. As Manchin quipped, “I’ll be 71 years old in August; you’re going to whip me? Kiss my you-know-what!” Manchin may certainly have been scoring points with conservative West Virginia voters by standing up to the liberal leader of the Democratic Party, but being less dependent on national party money also gives former governors more leeway in general.

At the same time, our analyses allow us to reject several alternative explanations for the differences between former governors and other senators, such as personality type, experience in other positions of leadership (such as business), and prior experience representing a statewide constituency. The differences we find seem to stem from the unique experiences of serving as governor and the fundraising base it allows them to develop.

Ultimately, electing former governors isn’t likely to break gridlock in Congress. But our research suggests the pronouncements of political independence from Romney, Bredesen and Scott may be more than just cheap talk.

Alex Keena is an assistant professor in the department of political science at Virginia Commonwealth University.

Misty Knight-Finley is an assistant professor in the department of political science and economics at Rowan University in New Jersey.