WASHINGTON -- As voters across the country head to the polls to vote in primaries ahead of this fall’s midterm elections, President Donald Trump has been eager to weigh in. 

  • Trump endorsing candidates in contested GOP primaries
  • His picks have been winning, or are leading 
  • President has endorsed 20 GOP candidates so far in 2018

In the last 14 contested Republican primaries where the president has endorsed a candidate, his pick has won or is leading, proving his nod has the power to move GOP voters behind his preferred candidate.

The president has been eager to leap into contested nomination fights, putting out endorsements via Twitter several times a day.

With a single tweet, the president is effectively deciding primaries. A prime example is his endorsement of Congressman Ron DeSantis for Florida Governor, taking him from underdog to clear frontrunner in his primary race. 

Thanks to the internet age, the president is intervening in a way his predecessors never could. 

“What we also didn’t have was Twitter before when George Bush was in office," said Brian Walsh, a veteran Republican Strategist with Rokk Solutions. "They also didn’t necessarily have the platform that President Trump does today, and he’s putting that to use.”

However, the president’s role as the party kingmaker has caught some candidates and Republican operatives off guard.

"In certain cases, it’s certainly frustrating for party officials who are carefully managing some of these races," Walsh explained. "There isn’t necessarily a process of vetting certain candidates.”​

President Trump's endorsements at times have gone against state and local party leadership. According to Kyle Kondik with the University of Virginia Center for Politics. Prime examples of this are playing out in gubernatorial races in Kansas and Florida.

“You have a situation where the president is coming in to endorse someone like Chris Kobach in Kansas or Ron DeSantis in Florida -- those are not necessarily the candidates that I think establishment Republicans would want in those races," Kondik said.

President Trump has already endorsed more than 20 Republican candidates running for office in 2018. While many have been successful in their primaries, some experts worry about how they’ll perform in the general election.

“You look at Kansas for example or Florida. Arguably, you have a candidate who is not the strongest candidate to face the Democrat in the fall winning some of these primaries," Walsh said.

In more purple states like Florida, a presidential endorsement could have consequences later.

“If you’re going to embrace the president and the president is going to embrace you in a primary, that creates some tailor-made material for the general election," Kondik said. "You'll probably see the Democrats revive that strategy and use Trump against Republicans particularly after some of these primaries are over.” 

This is only the beginning -- President Trump recently has vowed to campaign six or seven days a week this fall for vulnerable Republican candidates.