Live updates: Democrat Fetterman makes surprise appearance at GOP convention

The Republican nominee for Senate in North Carolina and former RNC Chair Michael Whatley used his time on the convention stage to praise Republican tax cuts and slam "radical Democrats" for high costs.

"With the November election just 55 days away, let's talk about what Republicans have accomplished for working families, and what radical Democrats have stood against," Whatley said.

"Under President Trump's leadership, Republicans passed the 'Working Families Tax Cuts' and put thousands of dollars back into the hands of families and seniors. My opponent, Roy Cooper, opposed this bill," Whatley said, drawing boos from the crowd.

Whatley is locked in a competitive race against former North Carolina Gov. Roy Cooper as Democrats view the battleground Senate seat being vacated by retiring Sen. Thom Tillis as one of their best pickup opportunities this year.

-ABC News' Halle Troadec

GRAPEVINE, Texas -- Down the road from the GOP midterm convention in Dallas, Mike Njenga's trucking company is struggling. His diesel fuel expenses have skyrocketed because of the Iran war -- forcing him to take trucks off the road and pass price hikes to customers.

Njenga voted for Trump and has been happy to back Republicans for years. But he told ABC News' Rachel Scott he is strongly considering voting for Democrat James Talarico for Senate in November.

"Whether he's conservative, whether you're liberal, at this point, all I care [about] is economics," he said. "I want to make sure things I can survive in business. I want to make sure I'm going to be able to feed my kids."

Njenga's situation underscores the challenge Republicans face as they try to excite their base heading into the fall, and how Trump's handling of the economy and Iran war loom over all other issues.

Asked how he thinks Trump is handling the economy, Njenga replied, "Just looking at what is going on right now in the world and between the tariffs and the war in Iran, it's not very encouraging. I am disappointed."

-ABC News' Benjamin Siegel

People have dubbed the midterm convention the "Trumpapalooza" as the president is expected to be at the center of the celebration.

So far, it looks like it -- photos of Trump line the walls at the American Airlines Center.

-ABC News' Hannah Demissie

Trump said he anticipates a "tremendous crowd" at the convention but said some Republicans aren't coming due to a lack of space.

"I think we're going to have a tremendous crowd tonight. Sold out. Looks very big. Looks very exciting, and we're going to explain what we've done," Trump said as he was departing Joint Base Andrews for Dallas.

Asked by ABC's Mary Bruce about Republicans in key races who decided not to attend the convention, Trump said that "everybody is coming."

Trump argued that some people were not coming because there wasn't space, saying "we don't have room for 500 politicians."

"We have room for the ones that have a close race if they're slightly behind or slightly ahead or tied, but we don't have rooms for people that are 35 points up and don't need to be there," Trump said.

American Airlines Center in Dallas, where the convention is being held, can hold up to 20,000 people, according to American Airlines.

-ABC News' Isabella Murray and Nicholas Kerr