

I think it’s important to put it in context: the Democrats are hemorrhaging support from their base who thinks they should be doing more to resist this administration. That does not mean they are losing support in favor of Republicans.
Meanwhile Trump is only losing a tiny amount of support because his base is a cult of personality that worships him. They won’t turn against him until he’s hurting them so directly that they can’t rationalize it as somehow being Obama’s fault. But many of them are delusional enough that they will never abandon their fealty so matter how much he harms them.
More likely it’s so they can use their personal phone to show the conversation to their Russian bosses without needing to bypass security measures.