Last week, a Democrat seeking his party’s nomination for a congressional race in Colorado secretly recorded House Democratic Whip Steny H. Hoyer of Maryland trying to push him out of the race — and released the recording to the Intercept. Conversations between party elites and prospective candidates do not usually leak to the media. But both Democratic and Republican party leaders and staff regularly try to clear the primary field for the candidates they believe most likely to win in House and Senate general elections.

These efforts pay off for party elites. As I show in my new research, candidates are more likely to stay in the race and to win the party’s nomination when they receive either the tacit or explicit backing of party elites.

Here’s how I did my research

Parties rarely explicitly endorse candidates in party nomination contests. That means we can’t just tally up endorsements of primary candidates to know which candidates the parties prefer.

To discern the party’s preferred candidate, I start by thinking about a party as a network of elites — including elected party officials, party staff and wealthy donors. Then I use patterns of financial contributions from donors to candidates and their parties to measure how connected candidates are to party elites.

I started by compiling a list of every candidate who declared his or her candidacy for the Senate or the House between 2004 and 2014 and then filed paperwork with the Federal Election Commission to form a campaign committee. To measure the level of party support for each declared candidate in the primary, I counted the number of donors who gave both to the candidate and to the party’s congressional or senatorial campaign committee.

This measure does a good job capturing media portrayals of insider and outsider candidates. For example, in 2010, Republicans Lt. Gov. Jane Norton and Weld County District Attorney Ken Buck faced off against each other in the Colorado Senate GOP primary. Reporters branded Buck the outsider. That’s what I found as well. While Buck and Norton both raised more than $2 million from individual donors, Buck received only 58 donations in the primary from donors who also gave to the national party, while Norton received more than 200. On average between 2004 and 2014, party-supported candidates received over five times as many donations from party-connected donors than did candidates without party support.

For each candidate, I also recorded their share of the primary election vote. If a candidate withdrew before the primary, I noted the date on which the candidate dropped out of the race.

Here are three key takeaways from my study of party elites in primaries.

1. Parties are most active in swing districts

Party elites are most likely to intervene in the races most likely to be competitive in the general election — where national party committees want to select the candidate more likely to give the party a better chance at winning the seat. In contrast, parties rarely get involved in races for either safe or unwinnable seats.

2. Party support keeps candidates in the race

Support from party-connected donors matters — regardless of a candidate’s fundraising success or past elected experience. The more party-connected donors a candidate can attract, the more likely the candidate will stay in the race for longer. Indeed, for the Senate races I study, over the course of the whole primary election cycle, a candidate with no party support is almost 50 percent more likely to drop out of the race as a candidate with higher levels of party support. Results are very similar for competitive House races.

Party elites are not just jumping on the bandwagon of the top candidates. Once the party supports a candidate, he or she tends to start raising more campaign funds. But just because a candidate is good at fundraising doesn’t help predict future party support.

3. Party support helps preferred candidates win

Almost 80 percent of Senate and 70 percent of House party-supported candidates win their primary races. The figure below shows that as the level of party support increases, a Senate candidate is more likely to win the nomination. A candidate with high levels of party support is almost 60 percent more likely to win the primary election than a candidate with no party support.

Greater support from party donors helps a candidate win the primary

Why is party support so helpful to candidates?

First, party support offers critical funding for nascent campaigns. As one fundraiser explained to me, “If all of a sudden someone in the party sends you a message saying this is the guy we think is best-positioned, well, you’re more likely to get a big check.” Party elites are well-connected and pick up on signals from the party about who they should support.

Second, party support fosters important media connections for primary candidates. One former state party chairman told me that “one of the biggest resources the party can bestow is perceived credibility. They’ll drop the person’s name to [their media connections] … they can create the media hype and the perception that they’re a leading player.”

Third, support from party elites helps improve the quality of the candidate’s campaign staff. One party staffer mentioned a primary candidate’s campaign that had asked party leadership to recommend someone for a critical campaign position. Party leaders weren’t confident that candidate could win the general election, so they intentionally recommended a staffer whom party leaders perceived to be the least capable.

Will these efforts pay off for the parties in November?

In the early 20th century, progressive movement activists pushed states to adopt primaries to wrestle nominating power away from party bosses, believing that would return power to voters.

A century later, party elites still influence the selection of nominees. The only thing unusual about Hoyer’s efforts was that they were leaked.

Hans Hassell is an assistant professor of politics at Cornell College and the author of The Party’s Primary: Control of Congressional Nominations.