When you see a .gov domain, you're looking at a site that belongs to an official U.S. government entity. hickenlooper.senate.gov is exactly that — the website for Senator John Hickenlooper. Government domains aren't available to just anyone; they're tightly controlled and verified. So the short answer to 'is hickenlooper.senate.gov safe' is yes, it's legitimate.
That said, the site is currently returning an access denied error if you try to visit it from automated tools or certain browsers. That's likely a temporary security measure, not a sign the site is fake. If you need to reach Senator Hickenlooper's office, the official contact information is available through the U.S. Senate website. For now, there's no reason to think the site itself is a scam — the domain and its security setup all point to a genuine government presence. Just be aware you may not be able to browse the site normally until the access restriction is lifted.