they do have subpoena power, but they do NOT with opened and on going official investigations, until after the investigation is complete.
They will get their chance after the on going investigation is completed.
THIS HAS ALWAYS BEEN the rules and regs and protocol.
What these congress critters are doing, breaks all rules and protocol, and is bordering on obstruction of an official investigation.
Fine, but again, what IF you're wrong?
What if the investigation is just a show?
What if it's ALL about keeping YOU distracted and polarized, while the thief picks your pocket?
And besides, it's common knowledge that The DOJ and FBI can make a guilty sinner out of Mother Theresa.
When you have that kind of power, you can find "dirt" on a 2 year old and use it to bring charges, then offer an "escape path", if you "cooperate" (for example: say what they want you to say)
AND....If you're so worried about Russian influence, how do you know for certain that the Russians aren't manipulating Mueller, Rosenstein and Sessions? The media told you Trump was a Russian agent....and you believed it. C'mon.