Donald Trump cancelled, and then promptly uncancelled, two in-person rallies in Kansas and Iowa this weekend as polls suggest US midterm election races in the previous Republican strongholds could go down to the wire.

On Thursday, just five days before election day, the Republican National Committee (RNC) announced the president would no longer host the Kansas and Iowa rallies and instead participate in “a large number of tele-rallies”. The RNC claimed it felt it was in a “strong position” in Kansas and Iowa.

But on Friday morning, a source familiar with the matter said the rallies were “back on” and rearranged to accommodate the 19 tele-rallies Trump is also participating in.

With control of the US Congress on the line, next week’s midterm elections amount to a referendum on Trump, who has repeatedly urged voters to pretend he is himself on the ballot, as his approval ratings continued to decline. Democrats are hoping to capitalize on growing discontent with Trump to retake the US House of Representatives, and also the Senate.

It is unclear whether Trump anticipated rearranging the Kansas and Iowa rallies, or if it was unexpectedly readded to his schedule.

Trump told reporters on Thursday that he believed Republicans would have “a strong Tuesday night”, and did not feel like he had to go to Kansas. But he also lashed out at a Reuters reporter who asked whether the initial change of plans was because Trump was sick of traveling across the country.

“Oh, you’re sick to ask that question. You are sick,” Trump told the reporter, accusing the reporter of being “way out of shape” and calling him “disgusting”.

Despite Trump and the RNC’s statements of confidence, Democrats have grown increasingly confident in recent months that they might flip seats in traditionally red states, in part because many voters are disgruntled with Trump’s handling of the cost of living – exacerbated by his war on Iran.

In a Guardian/Harris poll of roughly 2,000 adults, most respondents said the cost of living and government corruption were top issues heading into next week’s election, mirroring findings from other polls.

“I’m not going to Kansas because [Republican senator Roger Marshall] is doing very well,” Trump claimed on Thursday. But polls show a slim margin between the Republican and Democratic Senate candidates in Kansas – which has not sent a Democrat to the US Senate in 96 years – and Democrats have a small edge over Republicans in the Iowa gubernatorial and Senate races.

Trump’s tele-rallies, taking place on Saturday, will target 19 states, including those with competitive Senate races such as Alaska, Iowa, Kansas, Michigan, Nebraska, Ohio, Texas and South Carolina.

It will also target states with competitive House or gubernatorial races such as Alabama, Arizona, Colorado, Florida, Louisiana, Montana, Nevada, New Mexico, New York, Pennsylvania and Virginia.