If you're wondering whether sanders.senate.gov is safe to visit, the short answer is yes. The .senate.gov domain extension is exclusive to official U.S. government entities, and this site has been registered since 2007. That's about as solid an identity signal as you can get.
Because this is a government site, you shouldn't expect to see a privacy policy or terms of service in the same way a commercial site would have them. The automated analysis didn't find an about page or contact details in a recent archive snapshot, but that's likely because the snapshot couldn't fully render the live homepage. The live site itself blocks automated bots, which is standard for government websites.
What matters most for a site like this is security and reputation, and both are excellent. The connection is encrypted, the site has never appeared on any blacklists, and it's been archived online for nearly two decades. If you're looking for official information from Senator Bernie Sanders, this is the real deal. You don't need to worry about scams or fake sites here.