JD Vance's win in Ohio shows that Trump still has an immense sway over GOP voters

In moving the needle on vital GOP races, the power of a highly sought-after Trump endorsement was demonstrated by the primary win of Republican JD Vance in Ohio.

On Tuesday, Vance was declared the winner of Ohio's Republican primary with 32% of the vote and will run as the GOP candidate for an Ohio Senate seat over Josh Mandel.

The extent to which the former president still affects Republican voters is a good measure of whether Trump's backing of a candidate still matters.

Even though a super-PAC was supporting him, he was trailing in the polls. After a clutch Trump endorsement, Vance moved up in the polls.

Local officials urged Trump to pick another candidate in the race. Even though he seemed to overlook previous comments about him, Trump himself suffered blowback from the Vance endorsement.

He has criticized Trump before. In an exchange with his college roommate, he said he thought Trump could be America's Hitler.

It appears that Trump's backing matters.

Donald Trump Jr., the president's son, said that "MAGA is alive and well, and the GOP best take notice and finally understand where the people are."

Dave Carney, a veteran national Republican consultant, told NBC News that dismissing Donald Trump as not a major factor in the party is crazy.

Bill Kristol, the director of advocacy organization Defending Democracy Together, said that when Trump endorsed Vance, he was third at 10% behind Mandel and Gibbons.

Without Trump's endorsement, Vance almost certainly stalls out at 10% and finishes fourth. Kristol said that when Trump talks, Republicans listen.

Advisers fear that a high-profile loss of a desired Trump candidate would call into question his image as the Republican kingmaker.

The former president has been giving out endorsements. Since leaving office, Trump has made 160 endorsements.

Georgia gubernatorial candidate David Perdue and Alabama Senate hopeful Rep. Mo Brooks are two of the candidates he has backed. When the congressman began flagging in his Senate bid, Trump withdrew his endorsement.

Glenn Youngkin did not campaign with Trump, but the former president claimed credit for high-profile wins by GOP figures. However, that did not stop Trump from endorsing Youngkin and giving a shout out to his supporters.

Tim Ryan is the Democratic candidate. Rob Portman is retiring from office.