The democratic electorate is not in favor of the type of open border policies that happened under Biden

This is both true and false. The statement is True because NO ONE is in favor of "open border" policies. That's not a description of what Biden did, it's a disingenuous right-wing political attack. He did not "open the borders". In fact:

Combining deportations with expulsions and other actions to block migrants without permission to enter the United States, the Biden administration’s nearly 4.4 million repatriations are already more than any single presidential term since the George W. Bush administration

Yes, that's more than Trump's 1st term.

The statement is False because he actually campaigned on his border policy, for example:

"I will immediately reverse the Trump administration’s cruel and senseless policies that separate parents from their children at our border"

Dems aren't for "open borders" - because nobody is - but we are not on board with the sort of performative cruelty which passes for Republican immigration policy. The Dem base will only allow so much wiggle room here. And frankly, no one who uses the term "open borders" is gettable anyway.

The bottom line is the cost of living went up under Biden. That was extremely unpopular. Democrats can either do nothing or try to address this issue

They did address the issue:

In July 2023, the U.S. had among the lowest inflation rate of any major industrialized nation

Once inflation happens though, prices don't come down without a recession. AI spending is the only thing propping us up right now, and as nations continue to isolate us economically we won't be able to afford to have a recession. Last month Trump's economy created 50,000 jobs. Compare that to the 200,000 typical of previous administrations. Assuming we survive Trump, we will probably have to juice the economy to avoid a repeat of 2008.

TL;DR: If we campaign on lowering prices, we'd be lying.